REACTION PATTERNS OF THE RETICULOENDOTHELIAL SYSTEM UNDER STIMULATION*

Louis Nico Marie Duysens (March 15, 1921-September 8, 2015): a leading biophysicist of the 20th century

Louis Nico Marie (L. N. M.) Duijsens (Duysens) was one of the giants in the biophysics of photosynthesis. His PhD thesis "Transfer of Excitation Energy in Photosynthesis" (Duysens, 1952) is a classic; he introduced light-induced absorption difference spectroscopy to photosynthesis research and proved the existence of reaction centers, introducing advanced methods from physics to understand biological processes. Further, it is his 1959-1961 seminal work, with Jan Amesz, that provided evidence for the existence of the series scheme for the two light reactions in oxygenic photosynthesis. In one word, he was one of the master biophysicists of the 20th century-who provided direct measurements on many key intermediates, and made us understand the intricacies of photosynthesis with a simplicity that no one else ever did. We present here our personal perspective of the scientist that Lou Duysens was. For an earlier perspective, see van Grondelle and van Gorkom (Photosynth Res 120: 3-7, 2014).

Magnetically controlled targeted micro-carrier systems

Magnetically controlled targeted drug delivery systems are aimed at concentrating drugs at a defined target site, with the aid of a magnetic field. This technique has been developed specifically for directing drugs away from the reticuloendothelial system (RES). Literature on this topic suggests that these delivery systems are capable of altering the distribution of chemotherapeutic agents in the body. Hence these delivery devices offer the possibility of improving the therapeutic efficacy of the associated drugs. This paper reviews the work done to date towards the development and evaluation of biodegradable and non-biodegradable magnetic targeted drug delivery systems and outlines their future prospects and limitations in cancer chemotherapy.

Liposome disposition in vivo II: Dose dependency

The dose-dependent disposition of extruded multilamellar (diameter approximately 1 micrometer) negatively charged liposomes containing entrapped [14C]inulin was studied in mice. Mice received 1500, 300, or 15 mumoles of liposomal lipid/kg iv. Carbon 14 levels were measured in the blood, liver, spleen, and carcass for 72 hr. A pronounced saturation effect, consistent with the known dose behavior of other colloids, was seen at early times; it was manifested by higher dose values in the blood and spleen but by lower liver values as the dose increased. This dose effect was attenuated in the liver but was maintained in the spleen at later times, and percent dose values approached plateau values in all tissues for all doses at later times. [14C]Inulin was used at the liposomal marker because of its inability to enter cells (or, presumably, leave them if delivered there by liposomes) in its free form. An early decline in carbon 14 levels (over the first 48 hr) was seen in the liver for the low and medium doses. Because of the known ability of blood factors to cause liposomes to leak their contents, this decline was interpreted as being a loss of [14C]inulin from extracellularly bound liposomes during this period. Moreover, the plateau carbon 14 levels at later times were interpreted as approximating the true level of intracellular inulin delivery by the liposomes.