Specific Expression of N-Acetylaspartate in Neurons, Oligodendrocyte-Type-2 Astrocyte Progenitors, and Immature Oligodendrocytes In Vitro

To test the specificity of N-acetylaspartate (NAA) as a neuronal marker for proton nuclear magnetic resonance (1H NMR) spectroscopy, purified and characterized cultured cells were analyzed for their NAA content using both 1H NMR and HPLC. Cell types studied included cerebellar granule neurons, type-1 astrocytes, meningeal cells, oligodendrocyte-type-2 astrocyte (O-2A) progenitor cells, and oligodendrocytes. A high concentration of NAA was found in extracts of cerebellar granule neurons (approximately 12 nmol/mg of protein), whereas NAA remained undetectable in purified type-1 astrocytes, meningeal cells, and mature oligodendrocytes. However, twice the neuronal level of NAA was found in O-2A progenitors grown in vitro. In addition significant levels of NAA were also detected in cultures of immature oligodendrocytes. Our data partly support previous suggestions that NAA may be a useful neuronal marker for 1H NMR spectroscopic examination of the adult brain. However, they also raise the further possibility that alterations of NAA associated with some specific brain disorders, particularly disorders seen in newborn and young children, may reflect abnormalities in the development of oligodendroglia or their precursors.     

Arguments for the use of physiological criteria for improving the salt tolerance in crops

Efforts to develop new crop varieties with improved salt tolerance have been intensified over the past 15–20 years. Despite the existence of genetic variation for salt tolerance within species, and many methods available for expanding the source of genetic variation, there is only a limited number of varieties that have been developed with improved tolerance. These new varieties have all been based upon selection for agronomic characters such as yield or survival in saline conditions. That is, based upon characters that integrate the various physiological mechanisms responsible for tolerance. Yet over the same time period, knowledge of physiological salt responses has increased substantially.Selection and breeding to increase salt tolerance might be more successful if selection is based directly on the physiological mechanisms or characters conferring tolerance. Basic questions associated with using physiological selection criteria are discussed in the paper. These are centred around the need for genetic variation, the importance of the targeted mechanism, the ease of detection of the physiological mechanism (including the analytical requirements) and the breeding strategy. Many mechanisms, including ion exclusion, ion accumulation, compatible solute production and osmotic adjustment have been associated with genetic variation in salt tolerance. Yet their successful use in improving salt tolerance, via physiological selection criteria, is largely non-existent. Consideration is given to the role of physiological criteria in the short and long term in improving salt tolerance. In several glycophytic species, particularly legumes, physiological selection based on ion exclusion from the shoots shows promise. Recent results for white clover indicate the potential for using a broad physiological selection criterion of restricted Cl accumulation in the shoots, with scope for future refinement based upon the specific physiological characters that combined result in ion exclusion.     

The effects of magnetic stabilization on the structure and performance of liquid fluidized beds.

Liquid fluidized beds containing porous magnetic ion-exchange particles with densities ca. 1.03-1.16 g mL-1 were examined. The effect of magnetic stabilization was studied, both in terms of bed physical characteristics and sorptive behavior. Maximum applied magnetic field strength was approximately 200 oersted. Breakthrough and pulse analyses were carried out with protein and acetone solutions, respectively, with liquid flow rates ranging from approximately 1 to 3 cm min-1. Acetone pulses in columns containing 7 mL of particles had plate numbers ranging from 2.5 to 18 for magnetically stabilized beds and from 7.8 to 20 for non-stabilized fluidized beds. Under any particular set of conditions, magnetic stabilization always resulted in poorer efficiency, both in pulse analyses and in protein breakthrough experiments.     

Q fever in maritime Canada.

Only nine cases of Q fever were recorded in Canada in the 20 years prior to 1978. In the 18 months from August 1979 to January 1981 the disease was diagnosed serologically in six patients from the Maritime provinces. All were epidemiologically unrelated and none had been exposed to animals. Five had pneumonia and one had chronic Q fever with probable prosthetic valve endocarditis. Three of the five pneumonia patients presented with signs and symptoms of an acute lower respiratory tract infection and were indistinguishable clinically from other patients with atypical pneumonias. The other two with pneumonia presented with nonresolving pulmonary infiltrates and complained of decreased energy. Four of the five pneumonia patients responded well to treatment with erythromycin; the fifth required two courses of tetracycline. The patient with chronic Q fever had a large amount of cryoglobulins in his serum and evidence of immune complex disease. These cases indicate that Q fever should be considered as a possible cause of atypical pneumonia in Canada.     

Locomotory characteristics of human lymphocytes undergoing negative chemotaxis to oral carcinomas

Using a continuous-time Markov chain theory technique to quantitate the interaction of patients' lymphocytes with their tumours, we have shown that negative chemotaxis is brought about by stationary state lymphocytes showing a high probability of moving initially in the appropriate direction. Analyses of the data strongly suggest that lymphocytes sense chemotactic gradients using a spatial receptor mechanism analogous to that proposed for polymorphonuclear leukocytes.     

A possible role for dehydrodihydroxylysinonorleucine in collagen fibre and bundle formation.

The concentrations of NaB3H4-reducible collagen cross-links were determined at the time when collagen fibres and bundles are observed in electron micrographs of connective tissue developing around the implanted Ivalon sponge in adult male rats. The highest radioactivity occurs with hydroxylysinonoreleucine and histidinohydroxymerodesmosine, and the lowest with lysinonorleucine, the reducible amounts of these cross-links remaining relatively constant as fibres and bundles appear. On the other hand, dihydroxylysinonorleucine amounts are low during the initial stages of connective-tissue formation and rise sharply as collagen fibres and bundles develop and collagen matures, as shown by increased resistance of insoluble collagen to digestion with bacterial collagenase. The bulk of hydroxylysinonorleucine and dihydroxylysinonorleucine is glycosylated, the former with galactosyl or glucosylgalactosyl residues and the latter with glucosylgalactosyl residues. The changing relationships between the amounts of 3H-labelled hydroxylysinonorleucine, glucosylgalactosyldihydroxylysinonorleucine and non-glycosylated dihydroxylysinonorleucine as fibres and bundles appear suggest three post-translational steps involving lysyl-derived cross-links in the organization of collagen into fibres and bundles.     

Structural states and transitions of carp hemoglobin.

The wide ligand affinity range previously observed for carp hemoglobin is bounded at both extremes by regions of constant affinity. Within these regions, pH, organic phosphates, and the extent of ligand binding have no effect on the measured affinity and the cooperativity of ligand binding is greatly reduced or absent. The rates of CO recombination to fully and partially unliganded carp hemoglobin, under various organic phosphate and pH conditions, are shown to reflect this behavior. Constant kinetic rates are seen to directly correspond to the regions of constant affinity. Therefore, these are taken to be single protein conformations, one of high and one of low ligand affinity. In the simplest view, these conformations represent the R and T states of a two-state model, and most of the properties of carp hemoglobin are explained quite well within this framework. Increases in either hydrogen or phosphate ion concentrations favor the stabilization of the low affinity structure of even fully liganded carp hemoglobin. We have studied the structural transition from high to low affinity by monitoring the absorption spectra of carp hemoglobins at constant pH as a function of organic phosphate concentration. We find that different spectra are induced in both carp methemoglobin and cyanomethemoglobin by inositol hexaphosphate addition. Furthermore, the dependence of the magnitude of the spectral changes on pH and organic phosphate concentration is the close agreement with that predicted from studies of the ligand binding properties of the molecule.