Modulation of locomotor activity by substance P in rats

The effects of intraperitoneally or intracerebrally (DA A-10 area) administered substance P (SP) on locomotor activity of rats were studied in an exact 12-h light/12-h dark cycle changing from dark to light at 6 a.m. SP was administered either at 11 a.m. (light phase, minimal locomotor activity) or at 7 p.m. (dark phase, maximal locomotor activity). The effects of 12.5 micrograms/kg SP intracerebral and 125 micrograms/kg SP intraperitoneal were very similar. In the light phase SP produces excitation but inhibition of locomotion in darkness. Hence, the effect of SP depends on the internal mechanisms controlling motor activity and tends to level off the spontaneous circadian oscillation. We found a long lasting SP effect during both the light and dark period. The present experiments led us to the conclusion that SP has a levelling effect on locomotor activity. Probably this effect might be explained as SP's action on the dopaminergic pathway or dopamine metabolism, because the dopamine content in neurons also has a circadian rhythm.     

Autoradiographic studies of glial proliferation in different areas of the brain of the 14-day-old rat

Cell cycle parameters, as well as the mode of proliferation of glial cells, in four different areas of the brain of the 14-day-old rat (cortex, corpus callosum, nucleus caudatus putamen and commissura anterior) were studied using different cell kinetic methods after injection of [3H]TdR and/or [14C]TdR. The duration of the S phase (tS) was found to be about 10 hr and that of the cycle time (tC) about 20 hr, tG2 is less than 2 hr and t(G2 + M) about 4 hr. These values are valid for glial cells in all four brain areas studied. However, the labelling index (LI) of the glial cells differs by a factor of 3, between 1.8 and 5.4% in the different brain areas. Accordingly, the growth fraction of the glial cell population in the four areas varies between 0.04 and 0.12. Glial cells (astrocytes as well as oligodendrocytes) proliferate according to a steady state system. Furthermore, the proliferation of glial cells is associated with continuous cell loss. After each mitosis about 3% of the daughter cells become pyknotic and die. In addition, a permanent exchange of glial cells occurs between the proliferating and non-proliferating pool.     

Evidence for dysfunction in the regulation of cytosolic Ca2+ in excitation-contraction uncoupled dysgenic muscle

In noncontracting, dysgenic murine muscle, excitation is uncoupled from contraction. To test whether the gene lesion is expressed as a defect in the regulation of the intracellular free Ca2+ levels, cultured normal and dysgenic muscle at various stages of development (proliferative myoblasts, early, late, and mature myotubes) were exposed to increasing increments (0.5-mM steps) of extracellular Ca2+ in ionophore A23187-Ca2+-EGTA-buffered media. Normal and dysgenic muscle at all stages (except myoblast) displayed contractures at approximately 500 microM free Ca2+ and higher. Experiments using finer increments of Ca2+ and different ionophore concentrations indicated an external Ca2+ threshold for contracture at 265 microM Ca2+ for early and late myotubes and 47-78 microM for mature normal and dysgenic myotubes. Low extracellular concentrations of calcium (14 microM and 0.76 nM) caused elongation of both normal and dysgenic myotubes. Mature cells were depolarized by exposure to increasing extracellular K+ and monitored by intracellular recording; normal and dysgenic myotubes showed similar reductions in membrane potentials. Depolarization to -35 mV elicited contractures in normal myotubes, but even depolarization to -9 mV in dysgenic cells elicited no response. Thus steady-state depolarization of dysgenic muscle does not cause contractures, which can, however, be elicited by increasing the intracellular free Ca2+. These results offer new evidence for a possible defect in the regulation of Ca2+ levels in dysgenic muscle.     

Stomatal movement in Zea mays: Shuttle of potassium and chloride between guard cells and subsidiary cells

Summary When stomates of Zea mays open K and Cl migrate from the subsidiary cells into the guard cells; when the stomates close both elements return to the subsidiary cells. Subsidiary cells function as reservoirs for K and Cl. Import of K and Cl into the guard cells and loss of both elements from the guard cells become observable 1 or 2 min after light is turned on or off, both when histochemical methods and the electron-probe microanalyzer are used for detection. Each stomatal complex of maize contains on the average 10±3×10^-13 gram equivalents (eq) of K and 4±1×10^-13 eq of Cl. Guard cells accumulate K in the light and CO₂-free air at an average rate of 10×10^-15 eq K per minute, and Cl at approximately half that rate.     

Genetic control of murine hemagglutinin formation to H-2.5

When B10.D2 (H-2^d) mice are immunized with lymphoid cells from C57B1/10 (H-2 ^d ) and their antisera tested against B10.A (H-2 ^a ) target cells, only antibodies to H-2.5 are measured. The same is true for immunization of DBA/2 (H-2 ^d ) mice when their antisera are absorbed with B10.D2 cells prior to testing. Irrespective of the dose of immunogen administered, the primary hemagglutinin response of B10.D2 mice is significantly lower than that of DBA/2 mice and (B10.D2 × DBA/2)F₁ hybrids, but the secondary responses are similar. The low responsiveness of B10.D2 mice appears to be determined by a single dominant gene with incomplete penetrance; the gene is not linked to eitherH- 2, Hc, or the immunoglobulin allotype loci. In addition, the H-2.5 hemagglutinin response is susceptible to nongenetic influences. When antisera from B10.D2, devoid of H-2.5 hemagglutinins, were assayed in a complement-mediated cytotoxic test, they contained almost as much anti-H-2.5 activity as did the antisera from DBA/2 mice or (B10.D2 × DBA/2)F₁ hybrids. The possibility is discussed that the locus responsible for the deficient primary hemagglutinin response of B 10.D2 may not be determinant-specific but may affect hemagglutinin responses in general.     

Coordinated changes in enzyme activities of phenylpropanoid metabolism during the growth of soybean cell suspension cultures

Variations in teh activities of several enzymes of phenylpropanoid metabolism were studied in fermenter-grown cell suspension cultures of soyben (Glycine max).Concomitant large increases and subsequent decreases in the activities of phenylalanine ammonina-lyase (EC 4.3.1.5), cinnamic acid 4-hydroxylase, and two isoenzymes of p-coumarate:CoA ligase occurred prior to the stationary phase of the cell cultures. These findings represent a further example of an interdependent regulation of these enzymes of the general phenylpropanoid metabolism.The increases in all of these enzyme activities could be further enhanced by illunination of the cells.No comparable light effects and no significant changes were observed for the specific activity of an S-adenosylmethionine:o-dihydric phenol m-O-mehyltransferase and for the overall rate of the two-step reduction of feruloyl-CoA to coniferyl alcohol. These enzymatic reactions therefore appear to be regulated independently of the enzymes of the general phenylpropanoid metabolism.     

Tagesperiodik,Revierverhalten und Beutefang der Geißelspinne Admetus pumilio C. L. Koch im Freiland*

Auf einer Fläche von ca. 40 × 60 m eines Regenwaldes bei Manaus/Amazonas wurden über 30 Admetus pumilio untersucht, sowie Temperatur, Feuchte und Helligkeit im Biotop registriert. Man findet immer nur ein Tier in einer Höhle am Fuß großer Bäume; nahezu jedes derartige Versteck ist besetzt. Der Aktivitätsverlauf zeigt im Freiland 3 Aktivitätsschübe: der abendliche dient der Nahrungsaufnahme, der nachmitternächtliche dem Verlassen des engeren Reviers zu Partnersuche oder zum Höhlenwechsel, der morgendliche zur Rückkehr ins Versteck. Der Aktivitätsbeginn gegen 16 Uhr ist endogen, das Aktivitätsende gegen 6.30 Uhr weitgehend exogen bestimmt. Der Rückzug in die Höhle am Morgen erfolgt bei 10fach niedrigerer Helligkeit als der Auszug aus dieser am Abend. Adulte Geißelspinnen behalten über mehrere Wochen die gleiche Höhle bei; beobachtet wurde bis zu 65 Tagen. Innerhalb eines untersuchten Umkreises von 7—10 m können sie sich hervorragend orientieren — vermutlich olfaktorisch. Die Beutefanghandlung wird beschrieben und die Orientierung hierbei analysiert. Zwei mechanorezeptorische Systeme werden nach- oder nebeneinander wirksam: Trichobothrien auf den Schreitbeinen leisten die Fernorientierung und dirigieren die Annäherung an die Beute bis in den Wirkungsbereich der Tastbeine, die die Orientierung im Nahbereich übernehmen, vor allem beim Packen der Beute. Die kutikularen Haarsensillen auf den Beinen werden kurz beschrieben.