Comparative biological characterization of Berenice and Berenice-78 strains of Trypanosoma cruzi isolated from the same patient at different times

The Berenice-78 strain of T. cruzi is very different from the Berenice strain isolated 16 years earlier from the same patient. The authors verified its high infectivity and low virulence for C3H inbred mice that survived the acute phase of infection. In these animals, it was verified that the tropism of parasites was more accentuated for cardiac and skeletal musculature and the parasitaemic level progressively increased with successive blood passages with posterior stability. In relation to Berenice strain the same characteristics were observed as described by Brener, Chiari & Alvarenga (1974). The increase in its virulence for albino mice was again demonstrated. The authors discussed the possibility of reinfection of the patient called Berenice and the importance of knowledge about T. cruzi strains of low virulence for laboratory animals.     

Effect of pH on Penetration of Naphthaleneacetic Acid and Naphthaleneacetamide Through Isolated Pear Leaf Cuticle

Penetration of naphthaleneacetic acid through enzymatically isolated upper pear (Pyrus communis L. cv. Bartlett) leaf cuticle increased as the donor pH was decreased. Naphthaleneacetamide penetration was not influenced by donor pH. The effect of pH on naphthaleneacetic acid penetration was reversible. Higher receiver (simulated leaf interior) pH favored penetration of naphthaleneacetic acid. Changes in the degree of dissociation, and hence polarity, as controlled by hydrogen ion concentration was the prime factor in the response of naphthaleneacetic acid to pH. At pH values lower than the pK (4.2 for naphthaleneacetic acid), the molecule was primarily undissociated, lipophilic, and penetrated into the cuticle; whereas, at pH values above the pK naphthaleneacetic acid was ionized, hydrophilic, and penetrated the cuticle with difficulty or not at all. Data presented are consistent with the hypothesis that naphthaleneacetic acid and naphthaleneacetamide penetration through the cuticle takes place by diffusion.     

Ion exchange properties of isolated tomato fruit cuticular membrane: Exchange capacity,nature of fixed charges and cation selectivity

Summary Isolated tomato fruit cuticular membrane, free of extractable materials, was titrated potentiometrically using various bases. Three dissociable groups were observed in the pH ranges 3–6 (0.2 meq g^-1), 6–9 (0.3 meq g^-1) and 9–12 (0.55 meq g^-1). The first group was tentatively assigned to-COOH groups of pectic materials and protein embedded in the membrane, the second to nonesterified-COOH groups of the cutin polymer and the third to phenolic-OH groups, such as non-extractable flavenoids present in the membrane, and to a small amount of-NH ₃ ⁺ groups of proteins. The cuticular membrane exhibited a behavior typical of highly cross-linked, high-capacity ion exchange resins of the weak-acid type. Ion exchange capacity increased with increasing pH and neutral salt concentration. At constant pH and salt concentration, the exchange capacity increased with increasing counter ion valence and decreasing crystal radius, e.g. [tris (ethylenediamine) Co]³⁺Ca²⁺>Ba²⁺>Li⁺>Na⁺>Rb⁺>N(CH₃) ₄ ⁺ . The cutin polymer exhibited a pronounced selectivity for Ca²⁺ over Na⁺ which increased with increasing neutralization of fixed charges. The large trivalent [Co(en)₃]³⁺ was preferred only at low equivalent ionic fractions in the polymer. These results are discussed in relation to the structure and function of cuticular membranes.     

STRUCTURE OF THE PEAR LEAF CUTICLE WITH SPECIAL REFERENCE TO CUTICULAR PENETRATION

Study of the pear leaf cuticle (Pyrus communis L. ‘Bartlett‘), in both intact and enzymatically isolated forms, has revealed that the cuticular membrane is separated from the underlying epidermal cell wall by a layer of pectic substances which extend into but not through the membrane. A layer of embedded birefringent waxes occurs towards the outer surface of the cuticular membrane. Platelet-like epicuticular waxes are deposited on the outer surface. The upper cuticular membrane is astomatous. The lower epidermis is stomatous, and the outer cuticular membrane is continuous with that lining the substomatal cavity. The lower cuticular membrane is also generally thicker than the upper, and both the upper and lower cuticular membranes are thicker over veinal than over mesophyll tissue. The birefringence frequently is discontinuous over anticlinal walls and over veinal tissue. The lower cuticle appears to contain fewer embedded waxes (as indexed by birefringence) than the upper. Enzymatic isolation of the cuticular membrane from the underlying tissues does not appear to cause any discernible change in structure as viewed with a light microscope. These findings are discussed in light of current knowledge concerning penetration of foliar applied substances into the leaf.     

QUANTITATIVE AND QUALITATIVE DIFFERENCES IN PLANT RESPONSE TO THE GIBBERELLINS

Wittwer , S. H., and M. J. Bukovac . (Michigan State U., E. Lansing.) Quantitative and qualitative differences in plant response to the gibberellins. Amer. Jour. Bot. 49(5): 524–529. Illus. 1962.—The comparative biological activities of gibberellins A₁ through A₉ were evaluated, over a wide concentration range and in several test systems. All gibberellins were effective in promoting stem elongation of dwarf peas (Pisum sativum), and, with the exception of A₈, epicotyl growth in Phaseolus vulgaris. Elongation of Cucumis sativus seedlings was strikingly greater with A₄, A₇, and A₉ than with the other gibberellins. With mutant dwarfs of Zea mays, A₅ and A₉ were the most active gibberellins for d₃ and d₅, and relatively ineffective compared to A₃ on d₁. Gibberellins A₂, A₇, and A₈ were less effective than A₃ on all dwarfs. Qualitative and quantitative differences among the gibberellins were noted on seedstalk elongation and flowering of Lactuca sativa, with A₃ the most active followed by A₁, A₇, A₄, and A₉. No flowering or seedstalk elongation occurred with A₂, A₆ or A₈. Parthenocarpic fruit growth in Lycopersicon esculentum was a function of dosage with all gibberellins. At the lowest levels, A₅ and A₇ were the most active, while at the highest levels all gibberellins with the exception of A₈ were equally effective. The results suggest a high degree of species and response specificity among the known fungal and higher plant gibberellins, and demonstrate the importance of utilizing a wide spectrum of plant responses and dosage levels in the biological assay of plant extracts for native gibberellins.     

Temporal dissociation of taste mixture components

Reaction times to salty and bitter tastes as single stimuliand in mixture were measured using response time deadlines rangingfrom 300 to 2500 ms. Salty reaction times were the same whethersalty was in mixture with bitter or a single stimulus, and theywere always shorter than bitter reaction times. Reaction timeto bitter was slower in mixture with salty than as a singletaste. Salty, alone and in mixture, was correctly identifiedon {small tilde}80% of the trials within 500 ms while correctbitter identifications did not reach similar levels until 1000ms. Bitter in mixture with salty never reached that level ofcorrect responding and correct responses actually decreasedslightly at response time deadlines of 2500 ms. The resultsshow that differences in taste onset latency are great enoughto allow identification of single tastes in mixtures.     

Some Physical-kinetic Considerations in Penetration of Naphthaleneacetic Acid through Isolated Pear Leaf Cuticle

The penetration of naphthaleneacetic acid (NAA) through enzymatically isolated pear leaf cuticle (Pyrus communis L. cv. Bartlett) is reported herein. Penetration of NAA increased with increasing lime and attained a steady state in approximately 20 minutes. The quantity of NAA penetrating was directly related to the concentration of the donor solution. NAA that penetrated the cuticle was shown to he unaltered. The Penetration of NAA from inside to outside is similar to that from outside to inside. Isolated stomatous lower cuticle permitted approximately 10-foId greater penetration of NAA than the astomatous upper cuticle. The penetration of NAA through isolated pear leaf cuticle is highly temperature dependent, exhibiting a temperature coefficient (Q₁₀) of about 5.6 between 15° and 25 C. The low quantities of chemicals penetrating through the isolated cuticle reported herein and elsewhere are considered to he a characteristic of the technique and not an absolute limitation of the cuticle. Cuticular penetration could account for physiological quantities of NAA entering the plant.     

Chloroplast-generated ROS dominate NaCl- induced K+ efflux in wheat leaf mesophyll

Mesophyll K⁺ retention ability has been recently reported as an important component of salinity stress tolerance in wheat. In order to investigate the role of ROS in regulating NaCl^-induced K⁺ efflux in wheat leaf mesophyll, a series of pharmacological experiments was conducted using MV (methyl viologen, superoxide radical inducer), DPI (an inhibitor of NADPH oxidase), H₂O₂ (to mimic apoplastic ROS), and EGCG ((−)-Epigallocatechin gallate, ROS scavenger). Mesophyll pre-treatment with 10 μM MV resulted in a significantly higher NaCl^-induced K⁺ efflux in leaf mesophyll, while 50 μM EGCG pre-treatment alleviated K⁺ leakage under salt stress. No significant change in NaCl^-induced K⁺ efflux in leaf mesophyll was found in specimens pre-treated by H₂O₂ and DPI, compared with the control. The highest NaCl^-induced H⁺ efflux in leaf mesophyll was also found in samples pre-treated with MV, suggesting a futile cycle between increased H⁺-ATPase activity and ROS-induced K⁺ leak. Overall, it is suggested that, under saline stress, K⁺ efflux from wheat mesophyll is mediated predominantly by non-selective cation channels (NSCC) regulated by ROS produced in chloroplasts, at least in bread wheat.     

Social determinants of health--a comparative study of Bosnian adolescents in different cultural contexts

This study investigated the effects of sociocultural contexts on health and the psychological well-being of immigrant adolescents, aged 15 to 18 years, originally from Bosnia and Herzegovina and now living as displaced persons either in Bosnia, or immigrants in Croatia and Austria. The study addresses the social determinants of health with a specific focus on five factors in the social environment that might have an influence on health status: gender, socio-economic status (SES), perceived discrimination and exposure to violence, social support and religious commitment. Dependent variables included self-rated health, a count of self-reported objective health problems and a range of indices of psychological well-being (somatic stress, anxiety, depression and self-esteem). The purpose of the study was to examine whether social risk factors have an effect on health, which factors mediate these effects on self-rated health and to assess whether these effects differ by gender Results indicate that perceived discrimination and violence are related to poor health through psychological stress as a major mechanism with stronger effects for girls in the study. Differences across the three socio-cultural contexts reveal the complexity and specificity of the relationships between analyzed factors as the association between discrimination and health was attenuated for some groups due to the protective resources of immigrants.     

Cation mediation of radical transfer between Trp48 and Tyr356 during O2 activation by protein R2 of Escherichia coli ribonucleotide reductase: relevance to R1-R2 radical transfer in nucleotide reduction?

A tryptophan 48 cation radical (W48(+)(*)) forms concomitantly with the Fe(2)(III/IV) cluster, X, during activation of oxygen for tyrosyl radical (Y122.) production in the R2 subunit of class I ribonucleotide reductase (RNR) from Escherichia coli. W48(+)(*) is also likely to be an intermediate in the long-range radical transfer between R2 and its partner subunit, R1, during nucleotide reduction by the RNR holoenzyme. The kinetics of decay of W48(+)(*) and formation of tyrosyl radicals during O(2) activation (in the absence of R1) in wild-type (wt) R2 and in variants with either Y122, Y356 (the residue thought to propagate the radical from W48(+)(*) into R1 during turnover), or both replaced by phenylalanine (F) have revealed that the presence of divalent cations at concentrations similar to the [Mg(2+)] employed in the standard RNR assay (15 mM) mediates a rapid radical-transfer equilibrium between W48 and Y356. Cation-mediated propagation of the radical from W48 to Y356 gives rise to a fast phase of Y. production that is essentially coincident with W48(+)(*) formation and creates an efficient pathway for decay of W48(+)(*). Possible mechanisms of this cation mediation and its potential relevance to intersubunit radical transfer during nucleotide reduction are considered.