Hippocampal mossy fibers and swimming navigation learning in two vole species occupying different habitats.

We showed previously for mice that size differences of the infrapyramidal hippocampal mossy fiber projection (IIP-MF) correlate with spatial learning abilities. In order to clarify the role of the IIP-MF in a natural environment, we studied the bank vole (Clethrionomys glareolus), adapted to a wide range of different habitats, and the root vole (Microtus oeconomus), living in homogenous grassland habitats with small home ranges. Morphometry on Timm-stained horizontal brain sections of six C. glareolus and six M. oeconomus revealed that the size of the entire mossy fiber projection was 42% larger in C. glareolus than M. oeconomus. C. glareolus had also an IIP-MF projection about 230% larger than that of the root vole. A sample of captured animals was then transferred to the laboratory (C. glareolus, n = 23; M. oeconomus, n = 15) and underwent testing for swimming navigation according to a standardized protocol used to assess water maze learning in about 2,000 normal and transgenic mice. Both species learned faster than laboratory mice. Overall escape times showed no differences, but path length was significantly reduced in C. glareolus, which also showed superior performance in a variety of scores assessing spatial search patterns. On the other hand, M. oeconomus showed faster swimming speed, and strong thigmotaxis combined with circular swimming. M. oeconomus also scored at chance levels during the probe trial, about as poorly as mutant knockout mice considered to be deficient in spatial memory. These differences probably reflect differential styles of water maze learning rather than spatial memory deficits: C. glareolus appears to be superior in inhibiting behavior interfering with proper spatial search behavior, while M. oeconomus succeeds in escaping by using rapid circular swimming. We assume that size variations of the IIP-MF correspond to a mechanism stabilizing hippocampal processing during spatial learning or complex activities. This corresponds to the ecological lifestyle of the two species and is in line with previous observations on the role of the IIP-MF.

[Investigations concerning the role of folic acid in the metabolism of autotrophic cells]. / Untersuchungen zur Rolle der Folsäure im Stoffwechsel autotropher Zellen.

The role of folic acid in metabolism was studied in mass cultures of Chlorella pyrenoidosa, especially with respect to its possible participation in early stages of photosynthetic CO2-fixation. Sulfonamides (sulfanilamide, sulfathiazole) were used as specific antimetabolites in the biosynthesis of folic acid.After 24 hours the number of cell divisions was much more diminished than the pigment and nucleic acid content of the cells. Significant inhibition of mass production did not occur before 48 hours. This difference in the sensitivity of cell division and mass production towards the antimetabolite leads to a definite increase in cell size.Antimetabolites administered together with (10(-6) mol/l) p-aminobenzoic acid or (10(-5) mol/l) folic acid cause no inhibition.The harmful effect of the sulfonamide is strictly reversible; the speed of recovery depends on the p-aminobenzoic acid concentration. (14)C-Fixation experiments gave no evidence for the participation of folic acid enzymes in primary processes of photosynthetic carbon uptake. The decline of the fixation rate may be interpreted as a secondary effect on the enzyme apparatus necessary for photosynthesis.The enormous increase of the sugar content in the individual cells indicates a general disturbance of the metabolism.