Free Fatty Acids in the Rat Brain in Moderate and Severe Hypoxia

Abstract: The effects of mild, moderate, and severe hypoxia on cerebral cortical concentrations of free fatty acids (FFAs) were investigated in artificially ventilated rats under nitrous oxide anaesthesia. No change occurred during either mild (arterial Po₂ 35–40 mm Hg) or moderate (Po₂ 25–30 mm Hg) hypoxia. The effects of severe hypoxia (Po₂ about 20 mm Hg) combined with hypotension (mean arterial blood pressure 80–85 mm Hg) varied with the EEG pattern and the tissue energy state. Thus, a major increase in total as well as in individual FFAs occurred first when EEG was severely depressed (almost isoelectric) and energy homeostasis disrupted. On a relative basis the greatest change occurred in free arachidonic acid. It is concluded that hypoxia is associated with an increase in the concentrations of FFAs in brain tissue, provided that tissue oxygen deficiency is severe enough to cause tissue energy failure. However, an increase in FFAs does not invariably accompany minor reductions in the adenylate energy charge (EC) of the tissue.     

Vitamin analysis with use of a yeast electrode

A vitamin B₁ (thiamin)-sensitive electrode has been devised by combining an oxygen electrode with a yeast-containing membrane. The assembly was used for assaying thiamin at concentrations down to 10^?11 gl^?1. The analytical procedure developed should allow the measurement of 10–20 samples per hour. The performance of the yeast electrode was improved when alginate membranes reinforced with a nylon network were used. An apparatus for preparing such membranes is described together with a magnetic membrane holder facilitating handling of membranes in combination with electrodes.     

Analysis of trace elements in animal tissues

Graphite furnace atomic absorption spectrophotometry is a method used for the measurement of low concentrations of manganese (ppb range). Despite the widespread use of this technique, there is considerable inconsistency concerning sample preparation and choice of instrumental parameters. In this paper, we determined manganese concentrations of National Bureau of Standards (NBS) bovine liver by both graphite furnace (Instrumentation Laboratory IL 555B) and flame atomic absorption following wet digestion of the sample with nitric acid. The following instrumental parameters for the graphite furnace were found optimal for the measurement of manganese in digested NBS bovine liver: inert gas flow=14 SCFH, drying temperature 100°C/15 s (step 1), 125°C/15 s (step 2), pyrolysis temperature 500°C/15 s (step 3), and 1000°C/15 s (step 4); atomization temperature 2250°C/10 s (step 5). For optimal results, the nitric acid concentration of the sample should be between 2 and 4M. There were no significant differences found for manganese concentrations determined by either peak height or peak area measurement. Additionally, no significant differences were found in manganese concentrations determined by flame or furnace methods. Assuming proper sample preparation and choice of instrumental parameters, values obtained for manganese concentration by graphite furnace and flame atomic absorption spectrophotometry are similar. Therefore, data obtained by these two methods can be compared directly.     

Effect of low temperatures on the phospholipase A2 activity of rat liver mitochondria

Phospholipase A2 is shown to be activated by freezing-thawing, possibly due to changes in the state of lipid bilayer under the effect of both the temperatures themselves and physicochemical factors formed in the low-temperature range.     

Effects of alkylating agents on lymphocytes from controls and from patients with Fanconi's anemia

Summary The frequency of sister chromatid exchanges (SCE) and chromosome aberrations and the dynamics of cell division in peripheral blood lymphocytes of four patients with Fanconi's anemia were studied after in vitro exposure to alkylating agents TEPA and mitomycin.SCE frequency was significantly increased even after very low doses of mutagens, while chromosome aberrations were significantly increased only after high doses (0.160 g/ml mitomycin and 10^-5 M TEPA). The responses of Fanconi's anemia cells and control cells did not differ significantly. The increased frequency of both SCE and chromosome aberrations was accompanied by gradual delay of cell division, which was most conspicuous in cells from patients with Fanconi's anemia.     

Effects of protease treatment on growth,morphology, adhesion,and cell surface proteins of secondary chick embryo fibroblasts

Several proteolytic enzymes have been studied with regard to their ability to induce DNA synthesis and cell proliferation in resting chick embryo fibroblasts. Of the enzymes examined, thrombin, bromelin, and trypsin exhibit potent mitogenic activity, elastase has significant but less marked activity, whereas thermolysin, papain, and α-protease are inactive. The enzymes were also tested for their ability to induce morphological change or to remove two iodinatable proteins of 250,000 and 205,000 daltons. Although the larger protein is removed by some but not all of the proteases examined, every protease tested removed the smaller cell surface protein. The ability of proteases to stimulate cell growth could not be correlated directly with removal of either of these cell surface proteins; however, loss of the smaller protein does correlate with the reduction of both cytoplasmic spreading and cell-cell interactions observed after protease treatment. A secondary, later event of migration of cells into clumps is observed in those instances when protease treatment did not result in a loss of the 250K protein. A role for each of these proteins in the processes of cellular adhesion is discussed.     

Detection of Mls-antigens in various mouse strains using a new method

Mice of strains CBA and BALB/c, when injected with lymphocytes from theH-2-compatible Mls-antigen-incompatible strains C3H and DBA/2, respectively, develop a reduced lymphocyte reactivity against cells of the injected strains as measured in the mixed lymphocyte culture (MLC). The mechanism of the development of a depression of the MLC response against Mlsantigens is unknown. In this investigation we have tested the MLC response of lymphocytes from CBA mice preinjected with C3H lymphocytes against cells from 12 different strains. It was observed that the response decreased against cells from strains C3H, AKR, and A/Sn. Infusion of CBA mice with AKR lymphocytes decreased their MLC response against the same three strains. In contrast, infusion of CBA mice with A/Sn lymphocytes reduced their MLC responses against strains C3H, DBA/2, and the congenic strains A/Sn, A.SW, A.CA, and A.BY. BALB/c mice which were infused with DBA/2 lymphocytes developed reduced responses against DBA/2, C3H, and AKR. On the basis of these results we propose that mice of our strains C3H and AKR possess a common Mls-antigen which is strongly stimulatory, and that DBA/2 mice possess a second Mls-antigen which is also strongly stimulatory. The congenic strains A/Sn, A.SW, A.CA, and A.BY, which have differentH-2 complexes, possess a third Mls-antigen which is less stimulatory. The Mls-antigens of the strains listed above seem to exhibit extensive immunological crossreactivity.     

Heterologous expression of murine lymphotoxins in Escherichia coli and preparation of antibodies]

Genes encoding fragments of polypeptide chains of murine lymphotoxins (LT), namely, LT-alpha truncated from the N-terminus and the LT-beta extracellular domain, containing N-terminal hepta- and hexahistidine epitopes, respectively, were expressed in E. coli cells. The recombinant proteins purified by metallochelate chromatography were used to obtain polyclonal antibodies that specifically recognize murine LT.