Affinity thermoprecipitation of trypsin using soybean trypsin inhibitor conjugated with a thermo-reactive polymer,poly(N-vinyl caprolactam)

The soybean trypsin inhibitor conjugate with a thermo-reactive water soluble polymer, poly(N-vinyl caprolactam), was successfully used for thermally induced affinity precipitation of trypsin. The validity of the developed procedure was proven by a model separation of trypsin from dilute solution containing a large excess of bovine serum albumin.     

Nonuniform size distribution of nascent globin peptides, evidence for pause localization sites, and a cotranslational protein-folding model

Examination of nascent globin peptides accumulatingin vitro during globin synthesis in rabbit reticulocyte lysates was carried out. A view was supported that nonrandom distribution of codons with different usage frequencies in mRNA may determine the messenger's translation kinetics. Regions of reduced translation of - and -globin polypeptide chains were localized, and the cotranslational protein-folding model suggested previously was substantiated. An active conjunction of synthesis and folding of proteins was proposed as one of the main destinations of a translation nonuniformity.     

Effects of t-butyl-4-hydroxyanisole and other phenolic antioxidants on tumoral cells and Trypanosoma parasites

The antioxidant food additives 2(3)-tert-butyl-4-hydroxyanisole (BHA), 2,6-di(tert-butyl)-p-cresol (BHT) and the methyl and propyl esters of gallic acid inhibited Trypanosoma cruzi culture growth and oxygen consumption. The I50 values for growth and oxygen uptake with BHA were 0.284 and 0.400 and for BHT 0.083 and 0.235 mM, respectively. Moreover, BHA inhibited the respiration of several tumor cells, as well as of the procyclic and bloodstream trypomastigote forms of T. brucei brucei, with I50 in the range 0.29-0.52 mM. Inhibition of the parasites' oxygen uptake by BHA was not of the pure Michaelis-Menten type, but may be of a mixed form. It is postulated that these compounds are inhibitors because they resemble ubiquinone.     

Effect of nitrogen form on the growth and nitrate concentration of lettuce

Summary A pot experiment with lettuce involving three N forms each at six application levels, showed that lettuce can be grown satisfactorily with a very low nitrate content when supplied with ammonium sulphate and a nitrification inhibitor. For plants growing on nitrate N, the optimum midrib sap nitrate concentration as maturity approached was about 1400 mg/1 NO₃-N. Large losses of mineral N were observed from the peat medium, even in the absence of plants. A relationship is presented which would enable a lettuce grower to estimate whole-shoot nitrate concentration from a quick test of midrib sapi.e. NO₃-N (mg/kg in fresh shoot) =0.14×NO₃-N (mg/l in sap). Tipburn was worst at intermediate levels of applied N, and was less serious with pure ammonium nutrition than with nitrate.     

On the population dynamics and ecology of the shrimp species (Crustacea,Decapoda, Natantia) in the Central Amazonian river Tarumã-Mirim

Summary Collections over four years in the habitat of submerged litter show that shrimps are abundant the year round. Mean densities vary from 5–45 animals/m² of litter habitat. Finegrained density distribution within litter sites is highly clumped, but coarse-grained distribution in any given month between litter sites along the river is grosso-modo random.Density and species distribution are a function of the annual cycles of inundations. Of the five species (of a total of seven in the area) that were found to be breeding in the litter habitat it could be established that reproduction is restricted to the period of rising and highest water levels. Reproduction is low in all species, namely below 20 eggs per egg batch with essentially a single generation per year.Breeding ecology in relation to the litter habitat is briefly discussed.This project was supported jointly by the CNPq (Brasilian Research Council), by the OAS (Organization of the American States) and by the SUFRAMA (Financing body of local government)     

The finding of Enterobius vermicularis eggs in pre-Columbian human coprolites

Enterobius vermicularis eggs were found in human coprolites collected in the archaeological site of Caserones, Tarapaca Valley, Chile, dating from 400 BC to 800 AD. The human pinworm had already been found in other pre-historic archaeological sites in America, and its introduction in this continent is discussed.     

Redescription of Scapholeberis echinulata Sars 1903 (Crustacea,Cladocera)

Scapholeberis echinulata Sars is rediscribed, based on type material of Sars (S. echinulata), Daday (s. erinaceus) and the author's own samples. A differential diagnosis with Scapholeberis spinifera Nicolet and S. mucronata O. F. Müller, S. microcephala Sars, S. kingi Sars and S. aurita Fischer is given.     

Epithelial transport parameters: an analysis of experimental strategies

A set of experiments was simulated on a computer version of the Koefoed-Johnsen & Ussing model for high-resistance epithelia. The results obtained were analysed according to procedures commonly applied to the analyses of experimental data and interpreted in terms of the model parameters. Although the computer model encodes a stoichiometry of 3:2 for Na-K exchange through the Na pump, the simulation of published experimental procedures yields different figures in almost every case. We show that ENa as originally defined by Ussing & Zerahn (Acta physiol. scand. 23, 110-127 (1951)) and as obtained from flux-ratio experiments has different values under different experimental conditions with unchanged system parameters and that it is distinct from ENa measured by other methods. We also show that unless the pump is saturated with internal Na an increase in the rate of pumping cannot cause a substantial increase in the rate of transepithelial Na transport.     

The Avoidance Response in Phycomyces

Phycomyces sporangiophores grow away from stationary objects, a phenomenon known as the avoidance response. Evidence is presented suggesting that a growth-stimulating gas is emitted from the sporangiophore and is then swept to the leeward side by air currents resulting in higher gas concentration on that side. The presence of a stationary barrier decreases the passive movement of the gas away from the leeward side. It is proposed that an increase of this gas on one side causes that side to grow faster. Indirect evidence suggests that the gas is water vapor.