Cytologic observations on the effects of metallocene dichlorides on human fibroblasts cultivated in vitro

The effects of the organometallic cytostatic agents titanocene dichloride (TDC) and vanadocene dichloride (VDC) and of the inorganic cytostatic drug cis-diamminedichloroplatinum(II) (DDP) on the morphologic appearance of human embryonal fibroblasts cultivated as monolayers in vitro were analyzed by light and electron microscopy. All three substances induced similar structural changes which consisted of nuclear as well as cytoplasmic alterations. Many fibroblasts enlarged but the nuclear volume increased more extensively than that of the cytoplasm. The nuclear envelopes underwent invagination so that segmented nuclei were formed and the nucleoli increased in size and density. Within the cytoplasm there was evidence of conspicuous protein synthesis, characterized morphologically by an increase in the size and number of mitochondria, Golgi apparatuses and of cisternae of the rER. The phenomena observed are interpreted as indicating unbalanced cell growth characterized by a selective inhibition of DNA synthesis, coupled with progressive RNA and protein syntheses.     

Transplantation of a time-signal in honeybees

Summary It has been possible — by transplantation of brain tissue (i.e. mushroom-bodies) — to perform an interindividual transfer of a learned time-signal in honeybees. The information of the donor bees becomes determinative for the temporal activity pattern of the recipients about 3 to 4 days following transplantation.As seen from histological investigations done in parallel, the donor tissue is treated as a xenograft by the recipient's organism including disintegration and encapsulation processes. These observations give evidence for a humoral transfer of information.The results are discussed from the point of view of the analysis of the mechanism of time reception.Dedicated to Prof. Dr. H. Autrum on the occasion of his 70th birthdaySupported by the Akademie der Wissenschaften und der Literatur zu Mainz, the Stiftung Volkswagenwerk and the Deutsche ForschungsgemeinschaftAll observations done were individual per hand registrations. We want to give thanks to all people in the department who helped us to do the experiments.     

Light-dependent conformational change at rhodopsin's cytoplasmic surface detected by increased susceptibility to proteolysis

Rhodopsin in bovine photoreceptor disk membranes was subjected to limited proteolysis by thermolysin, removing twelve amino acids from rhodopsin's carboxyl terminus. (1) The rate of proteolysis is significantly faster with rhodopsin following exposure to light than with unbleached rhodopsin, provided that the incubation conditions (pH, temperature) favor the formation of metarhodopsin II. (2) If the disk membranes are illuminated under conditions in which metarhodopsin I is the predominant photoproduct (pH 8.5, 0°C), no increase in the rate of proteolysis is observed compared to unilluminated membranes. (3) The light-induced increase in the rate of proteolysis is transient: it slowly decays in the dark to the original rate found for unbleached rhodopsin. The enhanced susceptibility to proteolysis appears to measure a conformational change at rhodopsin's cytoplasmic surface which is first exhibited at the metarhodopsin II stage. This and possibly other light-dependent changes may allow rhodopsin to mediate its signal as a light-receptor protein by binding to and activating certain rod cell enzymes.     

Stimulation of the anaerobic growth ofSalmonella typhimurium by reduction ofl-carnitine,carnitine derivatives and structure-related trimethylammonium compounds

In view of the development of al-carnitine deficiency, the metabolism ofl-carnitine and structure-related trimethylammonium compounds was studied inSalmonella typhimurium LT₂ by means of thin-layer chromatography (TLC).l-Carnitine, crotonobetaine and acetyl-l-carnitine stimulated the anaerobic growth in a complex medium significantly. The stimulation depended on the formation of -butyrobetaine. The reduction ofl-carnitine proceeded in two steps: (1) Dehydration of thel-carnitine to crotonobetaine, (2) hydrogenation of crotonobetaine to -butyrobetaine. The reduction of crotonobetaine was responsible for the growth stimulation. Terminal electron acceptors of the anaerobic respiration such as nitrate and trimethylamine N-oxide, but not fumarate, suppressed the catabolism ofl-carnitine completely. Glucose fermentation, too, inhibited the reduction ofl-carnitine but optimal growth with a high carnitine catabolism was achieved byd-ribose. The esters of carnitine with medium- and long-chain fatty acids inhibited the growth considerably because of their detergent properties.Abbreviations TLC thin-layer chromatography     

Rotating frame spin-lattice relaxation experiments and the problem of intramolecular motions of peptides in solution

The application of rotating frame spin-lattice relaxtion to the determination of the intramolecular motions in peptides is discussed, and results are presented on the application of ¹³C T_1p to peptide microdynamics in solution. The effective molecular rotational reorientation times at the amide and amino nitrogens may be derived from appropriate data onT_1p of the carbons adjacent to them. We also show by theoretical caculations that ¹H and ¹³C T_1p experiments of suitable ²H and ¹⁵N substituted peptides will allow intramolecular main- and sidechain motions, characterized by times in the range 10^?1–10^?6 sec, to be investigated.