The effects of crude oil on the growth of Spartinaalterniflora Loisel. and Spartina cynosuroides (L.) Roth

Greenhouse studies were conducted to examine the effects of crude oil on the growth of Spartinaalterniflora Loisel. and S. cynosuroides (L.) Roth from North Carolina. The way in which crude oil came into contact with the plant tissue and/or substratum was an important factor in determining the responses of both species to oil pollution. Plants recovered from a single application of oil to aerial tissue with relatively little impact on productivity. The presence of an oil layer on the surface of an overlying layer of water had little impact on existing aerial portions of S. alterniflora plants; however, regrowth following harvest was completely inhibited. Incorporation of oil into the substratum significantly reduced aerial productivity and regrowth of S. alternflora and S. cynosuroides. Observations suggest that decreased productivity and regrowth may have been caused by decreased root and rhizome growth. Regrowth potential of S. alterniflora grown in oiled substratum was greater in fine-textured marsh substratum than in sand substratum.     

Column cellulose hydrolysis reactor: Cellulase adsorption profile

Summary A column cellulose hydrolysis reactor was set up using a single passage of cellulase enzyme which was followed with a continuous percolation of buffer. Hydrolysis rates were found to decline precipitously upon the removal of the non-adsorbed cellulase components. By comparing specific activities of the cellulase before and after adsorption on the cellulose column, it was concluded that the adsorption efficiencies for the cellulase components decreased from exoglucanase (1,4--d-glucan cellobiohydrolase EC 3.2.1.91) to endoglucanase [1,4-(1,3;1,4)--d-glucan 4-glucanohydrolase, EC 3.2.1.4] to -glucosidase (-d-glucoside glucohydrolase, EC 3.2.1.21). Of the adsorbed cellulase components, the rate of endoglucanase leaching from the cellulose column was 20 times that for the exoglucanase despite the greater adsorption efficiency of the latter. By analysing the cellulase components which were bound and not bound by the cellulose column and comparing them with a purified exoglucanase enzyme on sodium dodecyl sulfate polyacrylamide gels, it was confirmed that the major cellulase component adsorbed to the cellulose column was an exoglucanase component. The resultant loss of other cellulase components from the reactor was probably the cause for the much reduced rate of cellulose hydrolysis when these components were flushed out of the column.     

Column cellulose hydrolysis reactor: An efficient cellulose hydrolysis reactor with continuous cellulase recycling

Summary The use of a column cellulose hydrolysis reactor with continuous enzyme recycling was demonstrated by incorporating a continuous ultrafiltration apparatus at the effluent end of the column reactor. Using this setup, over 90% (w/v) cellulose hydrolysis was achieved, resulting in an average sugar concentration of 6.8% (w/v) in the effluent stream. The output of the system was 1.98 g of reducing sugar/l/h with a ratio of 87% (w/v) of the reducing sugars being monomeric sugars. Batch hydrolysis reactors were less effective, resulting in 57% (w/v) of the cellulose being hydrolyzed. The output of the batch reactor was 1.33 g of reducing sugar/l/h with similar product concentrations and percentage of monomeric sugars. The ratio of reducing sugar/filter paper unit of cellulase activity for the column method was 69.1 mg/U as compared to only 21.2 mg/U for the batch reactor.     

Inhibition of sodium for sodium exchange by phlorizin in frog sartorius muscle

The effects of phlorizin (2 X 10(-3) mol X l-1) on the Na transport of frog (Rana esculenta) sartorius muscle were investigated in glucose-free medium. Phlorizin decreased the rate coefficient of 24Na efflux by about 40%. The degree of inhibition was comparable to that caused by ouabain (10(-4) mol X l-1). Phlorizin could evoke a further reduction in the 24Na efflux also in the presence of ouabain. The intracellular Na content of the phlorizin-treated muscles remained unchanged, in contrast to a 60% increase induced by ouabain. 42K uptake was not affected by phlorizin. Data indicate that the ouabain-sensitive Na-K pump was not involved in the action of phlorizin. At the same time, phlorizin failed to alter the residual 24Na efflux measured in Li-Ringer solution containing ouabain. When Na: Na exchange was restored by replacing Na into the washout solution in the presence of ouabain, the increase of 24Na efflux was significantly diminished by phlorizin. Phlorizin reduced the 24Na uptake into a compartment with a half time of 6 min by about 40% without affecting the intracellular compartment. The results suggest that phlorizin inhibits the ouabain-insensitive Na: Na exchange in a superficial Na compartment.     

Stability of neuronal and glial marker enzymes in post-mortem rat brain

The enzymatic activities in post-mortem rat brain kept at 4°C and at 25°C were determined for a number of enzymes localized in specific cell types in the central nervous system. Choline acetyltransferase (CAT), glycerol-3-phosphate dehydrogenase (GPDH), glutamine synthetase (GS), lactate dehydrogenase (LDH) and 2,3-cyclic nucleotide phosphohydrolase (CNPase) were found to be very stable at both 4°C and 25°C with only slight, if any, losses of activity being seen even at periods as long as 72 hr. Glutamic acid decarboxylase (GAD) activity was less stable than that of the other enzymes. In brains kept at 4°C GAD activity was stable out to 24 hr after which it began to decline rapidly to 65% of control at 72 hr. In brains kept at 25°C, GAD activity was stable for 6–8 hr and then began to steadily decline to 58% of control at 24 hr and 29% of control at 72 hr. Assuming that these enzymes have similar stabilities in post-mortem human brain, the effect of post-mortem delay in processing tissues may be of lesser significance than other factors with regard to the measured enzyme activities in human brain samples.     

Evidence for prehistoric cardiovascular disease of syphilitic origin on the Northern Plains

The identification of the treponemas among prehistoric Amerindian populations is problematic. This paper presents the evidence for the presence of cardiovascular disease of syphilitic origin on the Plains of North America during prehistoric times. Comparative data from modern populations is used to arrive at a diagnosis.     

Spectroscopic properties of protochlorophyll forms in Triton X-100 detergent micelles

Protochlorophyll (PChl) forms were performed in Triton X-100 detergent micelles. The concentration of Triton X-100 was 7·10^?4 M (above the critical micellar concentration); the concentration of PChl varied between 1.6·10^?5 and 1.8·10^?4 M. Absorption, fluorescence and circular dichroism (CD) spectra were registered. The absorption spectra were resolved into Gaussian components by computer analysis. PChl forms with absorption bands at 632–634, 638, 652–654, 663–664, 668 and 676 nm and with fluorescence emission bands at 634–636, 640–644, 652–655, 677–678, 686 and 694–696 nm were observed in micellar solutions of different PChl concentrations. The CD spectra showed a strong dependence on the concentration of PChl: positive CD signals or positive Cotton effects were observed in the vicinity of 650 nm. The intensity of these signals increased in parallel with increasing concentration of PChl. No CD signals were found in the region of the longer wavelength absorption bands. These data show that the PChl exists in many different forms in this system, and the spectroscopic properties of these forms are determined by different molecular interactions viz., interactions of PChl with Triton X-100 or water molecules and/or by the aggregation of PChl.     

Sensitivity to values of the rate constants in a neurochemical metabolic model

Equations were derived for the instantaneous relative sensitivities of reaction rates (controllability indices) and metabolite concentrations (response indices) to perturbations in the values of rate constants and were used to analyze the behavior of a model of in vivo glutamate metabolism in rat brain. Controllabilities of reversible reactions were found to increase as the values of the corresponding rate constants (i.e., the rate of approach to equilibrium) increased. Response indices generally declined with the metabolic distance between the metabolite and the rate constant, but they were unexpectedly high for reversible reactions with high controllabilities. The transient response of a given metabolite is most sensitive to reactions involving metabolites which are changing most rapidly relative to their respective pool sizes. Rapidly reversible reactions are most important for communication between metabolite pools.     

Specificity of the Na+-dependent monocarboxylic acid transport pathway in rabbit renal brush border membranes

The substrate specificity of a Na+-dependent transport pathway for L-lactate was studied in rabbit renal brush border membrane vesicles. Jmax for L-lactate transport was unaffected by the presence of a fixed concentration of two different short-chain monocarboxylic acids, while the apparent Kt(Ka) for L-lactate increased, and this is compatible with competitive inhibition. The inhibitor constants ("Ki"'s) for the transport pathway for the two solutes examined closely corresponded to the respective "Ki"'s derived from a Dixon plot. A broad range of compounds were then tested as potential inhibitors of L-lactate transport, and the "Ki"'s thereby derived yielded specific information regarding optimal substrate recognition by the carrier. A single carboxyl group is an absolute requirement for recognition, and preference is given to 3 to 6 C chain molecules. Addition of ketone, hydroxyl and, particularly, amine groups at any carbon position, diminishes substrate-carrier interaction. Intramolecular forces, notably the inductive effects of halogens, may play a role in enhancing substrate-carrier interaction; however, no correlation was found between pKa and "Ki" for the substrates examined. We conclude that a separate monocarboxylic acid transport pathway, discrete from either the D-glucose, alpha or beta neutral amino-acid, or dicarboxylic acid carriers, exists in the renal brush border, and this handles a broad range of monocarboxylates.