Notes: Abstract— The swelling of intact, exposed primate cerebral cortex perfused in vioo under, isosmotic conditions was a linear function of the concentration of K+ in perfusate over the range 25–117 mM. The K+-dependent swelling was manifested throughout the depth of the cerebral cortex studied and was associated with an increased content of chloride in the swollen tissue, despite the constancy of the concentration of external chloride. The swelling of the cerebral cortex was a linear function of the temperature of the perfusate over the range 15–38°C, despite the constancy of the concentration of external K+. Moreover, the content of chloride in the swollen cerebral cortex was a linear function of the temperature of the overlying perfusate, despite the constancy of the external concentration of chloride. The changes in the contents of Na+ and K+ in the swollen cerebral cortex perfused with solutions containing constant concentrations of external Na+ and K+ but differing in temperature suggested that the fluid of swelling in the tissue was rich in both K+ and CI-, as had been shown previously in vitro. Perfusion of the exposed, intact cerebral cortex in uiuo with K+-rich fluids usually involved the reciprocal reduction of the concentrations of Na+ in the perfusate to maintain isotonicity. When comparable reductions in the concentration of external Na+ were achieved by replacement with choline (instead of K+), swelling of the perfused, exposed cortex was significantly less than that attributed to isotonic, K+-rich but Na+-poor fluids. These observations suggested that it was the elevated levels of K+ rather than lowered concentrations of Na+ that promoted the swelling of the perfused cerebral cortex.The apparent rate of influx of 36Cl from the perfusate into the underlying exposed and intact monkey cerebral cortex in vivo was a linear function of the concentration of K+ in perfusate over the range 25–117 mM and conformed to Michaelis-Menten kinetics when plotted according to Lineweaver and Burk. Moreover, the apparent influx of chloride from perfusate into swollen cerebral cortex was a linear function of the percentage swelling of cerebral cortex over the range 6–30 per cent. However, the apparent rate of influx of chloride from perfusate into unswollen cortex was not consistent with the linear correlation already described for swollen cerebral cortex. One reason for this discrepancy was the reduction in the size of the true (inulin) extracellular space associated with the K+-dependent swelling of cerebral cortex in vivo. The anatomical locus for this K+-dependent swelling of cerebral cortex was an expanded glial compartment, as demonstrated by electron-microscopy. The parenteral administration (50 mg/kg) or local perfusion (5 mM) of acetazolamide inhibited the K+-dependent swelling of cerebral cortex in vivo. Moreover, administration of acetazolamide inhibited the K+-dependent increase in content of C1- and the K+-dependent rate of influx of 36Cl into swollen cerebral cortex. We have discussed the possible enzymatic basis of these K+-dependent alterations in content of fluid and chloride and transport of chloride in mammalian cerebral cortex in viuo.

Notes: Abstract— In monkeys we measured the steady-state concentrations of Cl− in endogenous CSF, in artificial CSF (which had equilibrated with the underlying exposed surface of the cerebral cortex but was not in diffusion equilibrium with endogenous CSF), and in arterial plasma. The ratio of the distribution of Cl− in artificial CSF to that in plasma was consistent with a passive Donnan distribution, whereas that ratio describing Cl− levels in endogenous CSF in comparison to those in plasma clearly exceeded theratio required for a passive, Donnan−type of distribution for Cl−. The kinetic analysis of the efflux of Cl− from blood into endogenous CSF and into artificial CSF (perfused over the exposed surface of the cerebral cortex) indicated that the rate of efflux of Cl− into endogenous CSF which was continuous with ventricular fluid was inhibited by acetazolamide [in confirmation of a similar finding described previously by Maren and Broder (1970)], whereas the rate of efflux of chloride from blood into the artificial CSF perfusate was uninfluenced by pretreatment of animals with acetazolamide. We have discussed the site of mediated (active) transport of chloride from blood into CSF in light of these findings.

Notes: The potential contribution of intercellular light reflectance to photosynthesis was investigated by infiltrating shade leaves with mineral oil. Infiltration of leaves of Hydrophyllum canadense and Asarum canadense with mineral oil decreased adaxial leaf reflectance but increased transmittance. As a result of the large increase in transmittance, infiltration caused a decrease in absorptance of 25% and 30% at 550 and 750 nm, respectively. Thus, intercellular reflectance increased absorptance in these species by this amount. In a comparison of sun and shade leaves of Acer saccharum and Parthenocissus quinquefolia, oil infiltration decreased absorptance more in shade than in sun leaves. This difference suggests that the higher proportion of spongy mesophyll in shade leaves may increase internal light scattering and thus absorptance. The importance of the spongy mesophyll in increasing internal reflectance was also evident in comparisons of the optics of Populus leaves and in the fluorescence yield of oil-infiltrated leaves of several sun and shade species. Oil infiltration decreased the quantum yield of fluorescence (Fo) by 39–52% for shade leaves but only 21–25% for sun leaves. We conclude that the greater proportion of spongy parenchyma in shade leaves increased intercellular light scattering and thus absorptance. Direct measurements with fibre-optic light probes of the distribution of light inside leaves of Hydrophyllum canadense confirmed that oil infiltration decreased the amount of back-scattered light and that most of the light scattering for this species occurred from the middle of the palisade layer to the middle of the spongy mesophyll. We were not, however, able to assess the potential contribution of reflectance from the internal abaxial epidermis to total internal light scattering in these experiments. Using a mathematical model to compare the response of net photosynthesis (O2, flux) to incident irradiance for control leaves of H. canadense and theoretical leaves with no intercellular reflectance, we calculated that intercellular reflectance caused a 1.97-fold increase in photosynthesis at 20 μmol m−2s−1 (incident photon flux density). This enhancement of absorption and photosynthesis by inter-cellular reflectance, without additional production and maintenance of photosynthetic pigments, may maintain shade leaves above the photosynthetic light compensation point between sunflecks and maintain the light induction state during protracted periods of low diffuse light.

Notes: An attempt is made to integrate recent continental seismic reflection, refraction, and geologic observations into a unified scheme of craton evolution.〈list xml:id="l1" style="custom"〉1Nascent continental crust of basaltic bulk composition is produced in island arcs. As with oceanic crust, Moho in this setting lies within the magmatic edifice and corresponds to a downward transition from dominantly mafic cumulate rocks above to dominantly ultramafic cumulates below. The petrologic crust/mantle boundary, lying ∼25 per cent deeper in the lithosphere, has no seismic expression, and corresponds to a depositional/magmatic contact between cumulate ultramafic rocks above and residual mantle (ultramafic tectonite) below. Both contacts are presumably extensively disrupted by magmatic injection.2Island arcs are amalgamated into continents at collision zones. Delamination of the lower mafic/ultramafic portion of the crust along with the mantle lithosphere during ‘hard’ collisions acts as a mechanical refining process that pushes the bulk crust toward intermediate composition.3Subsequent extensional collapse of the overthickened crust together with thermal re-equilibration of the lithosphere results in ‘youthful’ stable continental crust, which is ∼30 km thick with its top surface awash at sea level and has the bulk composition of andesite. This crust characteristically exhibits extensional features (half grabens) in the upper portion, and is prominently laminated in the lower portion due to the injection of modest amounts of basaltic magma in the form of sills during delamination. The Moho and petrologic base of the crust coincide in this setting and can correspond to either a ductile high-strain zone or intrusive contact separating mafic/intermediate composition material above from fertile mantle (lherzolite) below.4Subsequent ‘cratonization’ is the cumulative effect of episodic injection of the crust by mafic magma at intervals of hundreds of Myr (as manifest by the ubiquitous overlapping dike swarms of the Precambrian shields). This results in net long-term thickening of the crust by underplating, shifts the bulk crust back toward mafic composition, periodically produces a new deeper Moho and petrologic crust/mantle boundary that do not coincide, and through repeated dike injection disrupts pre-existing laminated reflectors. The first magmatic injection event ‘sweats out’ the light melting fraction in the pre-existing andesitic crust, producing voluminous granitic magmatism typified by the great Proterozoic anorogenic granite/rhyolite provinces. Subsequent injection events into refractory crust produce uplift with attendant erosional denudation of supracrustal sequences. The cumulative result is shield-type crust in which intermediate crustal levels are exposed over wide areas, crustal thickness commonly exceeds 40 km, average crustal velocity is somewhat higher than in younger stable crust, and the crust is commonly complexly reflective/diffractive throughout.

Notes: Mean yellow eel density and biomass in two adjacent shallow (mean depth c 1·5 m) lochs varied significantly between years. Temporal patterns of density, biomass and size were similar in both soft and rocky substrata in the lochs, although eels were consistently smaller in the latter habitat. In both substrata, average length and weight showed a non-significant inverse relationship with density, supporting the hypothesis of density-dependent regulation of the yellow eel population. Fyke net catches were size selective, catching no eels 〈30 cm long, and providing length-frequency information for silver eels. Fyke net catch per unit effort (CPUE) declined consistently each autumn but specific annual trends were different. When eel density increased, fyke net CPUE declined substantially.