Nonpolymorphic regions of p190, a protein of the Plasmodium falciparum erythrocytic stage, contain both T and B cell epitopes

Two conserved regions from the genetically polymorphic p190 molecule of the malaria parasite Plasmodium falciparum have previously been expressed in Escherichia coli as separate polypeptides (190.L and 190.M) or as a single fusion protein (190.N). In the present study we investigated whether human B and T lymphocytes recognize these conserved regions. The more amino-terminal region, 190.L (corresponding to residues 188-363 of the encoded protein sequence) reacted preferentially with sera from donors living in a malaria-endemic area. Also, EBV-transformed B cells, from a healthy donor living in a malaria-mesoendemic area, were fused with a human-mouse hybrid line (SPM4-0), yielding two hybridomas whose products recognized both 190.L and the fusion protein 190.N, but not the 190.M polypeptide. A large number of p190-specific T cell clones were obtained from PBMC of a noninfected donor, after in vitro stimulation with the recombinant fusion protein 190.N. The clones reacted with intact, parasite-derived p190, as well as either 190.L or 190.M. Four clones that recognized the more amino-terminal fragment also responded to infected E. According to these results the more amino-terminal conserved sequences of p190 have the requisites to be immunogenic in humans.     

Content of phenolic acids in callus culture of alfalfa (Medicago sativa): The effect of age and biochemical differentiation

Phenolic acids were separated into three fractions and determined by HPLC inMedicago sativa callus culture at the age of two, three and four weeks. The contents of free and especially of predominating ester-bound phenolic acids decreased with callus age to approx. 80 % while the content of phenolic acids nonextractable by methanol increased byca. 90 %. The proportion of benzoic acid derivatives rose from 15 to 21 % within four weeks. The determined difference in the contents of phenolic acids in the upper and lower parts of callus diminished with age. The content of bound forms was higher in the lower part regardless of the callus age. The content of free acids in two weeks old callus was half as high as in the upper part.     

The dependence of the frequency of recessive lethal and vital mutations inArabidopsis thaliana (L.)Heynh. on the concentration of N-nitroso-N-methylurea

The dependence of the frequency of recessive lethal (two groups), chlorophyll and morphological mutations on the mutagen concentration was determined in M₂ after subjection to N-nitroso-N-methylurea applied to seeds ofArabidopsis in three concentrations (0·05, 0·10 and 0·20mm). The observed frequencies were compared with the theoretically expected ones for the linear and for two exponential types of dependence, by using the t-test, according to the formulas m=k. C, m=k. C^3/2, m=k. C². No satisfactory agreement with any expected type of dependence was found when directly observed frequencies were used. Since a considerable deficit of mutation frequency was observed in high concentrations, the correction of frequency values was done with respect to the probability of occurence of double mutations. After such a correction, a clear exponential relation was found in both types of lethals and a linear one in chlorophyll and morphological mutations. The probable occurence of multiple mutations should be, therefore, taken into account if the dependence of mutation frequency on the concentration of mutagen is discussed.     

Changes in the radioresistance of bacteria after the inhibition of proteosynthesis in the preirradiation phase

The strain ofEscherichia coli WP₂ (try_v) was irradiated with UV light, at a dosage of 240 erg/mm. Proteosynthesis was inhibited by the elimination of the essential amino acid from the cultivation medium. Changes in radioresistance were followed during 45 minutes of starvation and during the subsequent 45 minutes of restitution after the addition of the essential amino acid. The radioresistance of the cells showed a linear increase immediately after the removal of the essential amino acids, proportional to the duration of the inhibition of proteosynthesis. The increase in radioresistance was shown to be reversible. After the addition of the essential amino acid there was an immediate decrease in radioresistance which was most marked in the first 15 minutes.     

Effect of Glutathione and N-Acetylcysteine on in Vitro and in VIVO Cardiac Toxicity of Doxorubicin

The effects of two sulfhydryl compounds, glutathione (GSH) and N-acetylcysteine (NAC), on the cardiotoxicity of doxorubicin (DXR) were tested on in vitro and in vivo models. DXR was administered to rats as 4 weekly i.v. doses of 3mg/kg. GSH (1.5 mmoles/kg), given i.v. 10 min before and 1 hr after DXR, was found to prevent the development of the delayed cardiotoxic effects of DXR, as assessed by electrocardiographic and mechanical parameters, as well as by histological examination of left ventricular preparations. In contrast, equimolar oral doses of NAC (1 hr before and 2hrs after DXR) were found to be ineffective. Both GSH and NAC prevented the negative inotropic effect produced by DXR on isolated rat atria. A good correlation exists between the cardioprotective effects of the two agents and their ability to enhance the non-protein sulfhydryl group content of the myocardium. Differences observed in vivo between GSH and NAC might be accounted for by pharmacokinetic factors.     

Effects of growth conditions on the resistance of some pathogenic and spoilage species to high pressure homogenization

R. LANCIOTTI, F. GARDINI, M. SINIGAGLIA AND M.E. GUERZONI. 1996. The effects of chemicophysical growth conditions such as pH, temperature and water activity ( a _w) on lethal high homogenization pressure effects on Listeria monocytogenes, Staphylococcus aureus, Escherichia coli and Yarrowia lipolytica were investigated. The results, though based on standard media, emphasize the importance of food system composition and its thermal history on the high pressure tolerance of the microbial population.     

Study of the reversibility of the water saturation deficit as one of the methods of causal phytogeography

Jedním z kritérií pro posuzování odolnosti rostiin v??i suchu je jejich schopnost sná?et vodní deficit ani? nastanou irreversibilní změny v jejich pletivech. Tato schopnost byla zkoumána metodikou, popsanou v p?edlo?ené práci. Listy některých xerothermních trav (druhy roduStipa, Melica atd.) vysýchaly za p?esně definovaných pokusných podmínek tak, ?e dosáhly r?zně odstupňovaného vodního deficitu. Potom byly roz?ezány na segmenty a ve speciálním ráme?ku dosycovány vodou. P?vodní deficit i jeho vyronání bylo sledvváno váhově. Výsledné hodnoty byly znázorněny graficky. Zatímco ztráta vody z list? během vysýchání probíhala v některých p?ípadech lineárně, k?ivka dosycování ukazovala charakteristický zlom, který indikoval, jak dalece byla ztráta vody nahraditelná, a kdy do?lo ji? k irreversibilním změnám. Ukázalo se, ?e ze studované série rostlin druhy typicky kontinentální mají schopnost doplňovat svou zásobu vody ad integrum i p?i zna?ném vodním deficitu. Rostliny s areálem spí? oceánického charakteru tuto schopnost nemají. Je pravděpodobné, ?e i tato vlastnost bude směrodatná p?i výkladu kausální fytogeografie.