Neuronal precursor cells in the rat hippocampal formation contribute to more than one cytoarchitectonic area.

We have tested the hypothesis that cell lineage restriction boundaries define the borders between cytoarchitectonic areas in the cerebral cortex. Clonally related cells were identified using a retroviral marking technique, and the dispersion of neuronal clones was examined with respect to the transitions between cortical areas. We chose to study the hippocampal formation because we found that clones of hippocampal neurons, unlike those in neocortex, are compact and readily identifiable in the adult and that transitions between areas in the hippocampus are sharp relative to the spread of a typical clone. We conclude, contrary to the hypothesis, that clones of neurons transgress the boundaries between areas in the hippocampal formation, that border-crossing clones are observed as frequently as would be expected if clones spread freely over the hippocampus with no constraint imposed by area borders, and that different types of pyramidal neurons, characteristic of different areas, may appear to a single clone. different areas, may appear in a single clone.     

Traditional treatment for mental illness in Africa: A review

The publication of The Quest for Therapy in Lower Zaire (University of California Press) by John M. Janzen (with the collaboration of William Arkinstall), and African Therapeutic Systems (Crossroads Press), edited by Z. A. Ademuwagun, John A. A. Ayoade, Ira E. Harrison and Dennis M. Warren, calls attention to recent research findings which indicate that mentally ill persons, particularly schizophrenics, may recover more rapidly and fully in non-industrialized societies than they do in industrialized ones. The books by Janzen and Ademuwagen et al. will be examined as contributions to a growing body of information on native African therapeutic practices. Evidence relating to the apparently benign course of psychosis in Africa will be examined, and various explanations for this pattern will be evaluated. Finally, some guidelines for future research will be suggested.     

Involvement of protease in L-glutamine control of nucleic acid and polyphosphate metabolism in cells transformed by 9,10-dimethyl-1,2-benzanthracene, SV40 and H-ras oncogene

Mammalian cells transformed with either 9,10-dimethyl-1,2-benzanthracene, SV40 or H-ras oncogene dramatically changed their ability to synthesize DNA and RNA and metabolize polyphosphate when L-glutamine was withdrawn from the growth medium or when heat shocked (growth at 42 degrees C). Untransformed, DNA and RNA synthesis decreased by 50-80% when glutamine was withdrawn, but polyphosphate accumulated whether or not glutamine was supplied. Heat shock did not alter this response. Transformed isogenic cells responded differently; at 37 degrees C, they decreased their synthesis of DNA and RNA if starved for glutamine, whereas at 42 degrees C, synthesis was optimal without glutamine. Transformed cells accumulated polyphosphate at 37 degrees C when starved for glutamine, but at 42 degrees C, no polyphosphate accumulated. This apparent non-dependence on glutamine by transformed cells when heat shocked was found to be due to the production of glutamine from serum proteins through induction of a protease(s).     

Effects of glycerol on microtubule polymerization kinetics

Steady state and kinetic studies of polymerization of purified microtubule protein show little effect of glycerol on the steady state level of polymerization, as demonstrated by measurements of critical concentration. The rates of polymerization and depolymerization are slowed in the presence of glycerol. This data indicates that the stabilization of microtubules by high glycerol is largely a kinetic effect rather than a shift in equilibrium. However, the apparent critical concentration for microtubule polymerization from crude brain homogenate is substantially higher in the absence of glycerol, and glycerol appears to protect microtubule polymerization against the action of endogenous inhibitors.     

Inositol 1,4,5-trisphosphate and the endoplasmic reticulum Ca2+ cycle of a rat insulinoma cell line

Regulation of endoplasmic reticulum (ER) Ca2+ cycling by inositol 1,4,5-trisphosphate (IP3) was studied in saponin-permeabilized RINm5F insulinoma cells. Cells were incubated with mitochondrial inhibitors, and medium Ca2+ concentration established by nonmitochondrial pool(s) (presumably the ER) was monitored with a Ca2+ electrode. IP3 degradation accounted for the transience of the Ca2+ response induced by pulse additions of the molecule. To compensate for degradation, IP3 was infused into the medium. This resulted in elevation of [Ca2+] from about 0.2 microM to a new steady state between 0.3 and 1.0 microM, depending on both the rate of IP3 infusion and the ER Ca2+ content. The elevated steady state represented a bidirectional buffering of [Ca2+] by the ER, as slight displacements in [Ca2+], by small aliquots of Ca2+ or the Ca2+ chelator quin 2, resulted in net uptake or efflux of Ca2+ to restore the previous steady state. When IP3 infusion was stopped, [Ca2+] returned to its original low level. Ninety per cent of the Ca2+ accumulated by the ER was released by IP3 when the total Ca2+ content did not exceed 15 nmol/mg of cell protein. Above this high Ca2+ content, Ca2+ was accumulated in an IP3-insensitive, A23187-releasable pool. The maximal amount of Ca2+ that could be released from the ER by IP3 was 13 nmol/mg of cell protein. The data support the concept that in the physiological range of Ca2+ contents, almost all the ER is an IP3-sensitive Ca2+ store that is capable of finely regulating [Ca2+] through independent influx (Ca2+-ATPase) and efflux (IP3-modulated component) pathways of Ca2+ transport. IP3 may continuously modulate Ca2+ cycling across the ER and play an important role in determining the ER Ca2+ content and in regulating cytosolic Ca2+ under both stimulated and possibly basal conditions.     

The factors limiting growth and survival of brown trout, Salmo trutta m.fario L. introduced to different types of streams

Fingerlings of brown trout ( Salmo trulta m. fario L.) were introduced to sections of different types of streams situated in natural catchments and those modified by Man's activity. At stations where environmental conditions were modified by such forms of impact as pollution, flow variability and impoundment, trout did not survive 5 months. In the natural river sections mortality rates increased downstream along the river continuum and were associated with increased predation. Growth rates in the upper reaches were primarily restricted by abiotic factors—temperature and trophic status: however, they were to a large extent modified by density-dependent regulation and intraspecific competition. The influence of the abiotic/biotic regulatory process, expressed as fish metabolic performance, is discussed as a framework for the determination of the carrying capacity of the riverine ecosystem.