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At least 19 recordsLinked to original sources
PubMed2026

Integrated Functional Characterization of Hemileia vastatrix Effector Candidates Reveals Coordinated Immune Suppression, Sequential Deployment and Compartment-Specific Targeting.

Coffee leaf rust, caused by the obligate biotrophic fungus Hemileia vastatrix, remains the most destructive disease of coffee worldwide. Although genomic and transcriptomic studies have identified a large number of candidate effectors, experimental evidence supporting their biological roles during infection remains limited. Here, we integrated functional assays, temporal expression profiling during coffee infection and subcellular localization analyses to investigate the biological properties of 44 H. vastatrix effector candidates (HvECs). Using the Pseudomonas fluorescens EtHAn effector delivery system in Nicotiana benthamiana, 15 HvECs consistently suppressed pattern-triggered immunity (PTI), indicating that immune suppression is a widespread property among the H. vastatrix effector repertoire, as assessed in this heterologous system. Five HvECs also attenuated AvrB-triggered effector-triggered immunity (ETI), and three suppressed both PTI and ETI, suggesting that a subset of HvECs targets conserved regulatory nodes shared by these interconnected immune pathways. Temporal expression profiling revealed sequential deployment of HvECs throughout infection, with distinct subsets predominating during pre-biotrophic development, host penetration or biotrophic colonization, consistent with stage-specific functions during fungal pathogenesis. Subcellular localization analyses further showed that HvECs preferentially accumulated in the nucleus or chloroplasts, compartments known as central hubs of plant immune regulation. This study provides the most comprehensive functional characterization of H. vastatrix effector candidates to date, establishes a biologically informed framework for prioritizing candidates for future identification of avirulence determinants recognized by SH resistance genes, and advances our understanding of how the coffee rust fungus orchestrates immune suppression across time and cellular space during pathogenesis.

Nicotiana↗
PubMed1978

High and low level tetracycline resistance in Shigella sonnei.

The results presented in this paper confirm the existence of two types of tetracycline resistance in Shigella sonnei. One group of strains had a high level of resistance to tetracycline and oxytetracyline, with a variable level of minocycline resistance. The second group had a lower level of tetracycline resistance and were sensitive to minocycline. After conjugation with E. coli K12 the selected E. coli transconjugants had the same levels of resistance as the parent Sh. sonnei strain, with one exception. Sh. sonnei 87 was resistant to a high level of tetracycline, but was able to transfer only low level resistance. It is suggested that Sh. sonnei 87 carriers two plasmids: pSU1, a conjugative plasmid conferring a low level of tetracycline resistance, and pSU2, a non-conjugative plasmid which confers a high level of resistance to tetracycline.

Microbial Sensitivity Tests↗
PubMed1977

Purification and characterization of adenosine nucleosidase from barley leaves.

Adenosine nucleosidase (adenosine ribohydrolase, EC 3.2.2.7) has been purified to a nearly homogeneous state from barley leaves. The enzyme is soluble in concentrated salt solution while it aggregates and precipitates at low ionic strength, factors which enabled a simple purification procedure to be carried out. A molecular weight of 66 000 +/- 3000 was estimated for the native enzyme by gel filtration. In sodium dodecyl sulphate polyacrylamide gel electrophoresis of the most purified fraction a single major band of polypeptide chains, with molecular weight of 33 000, was observed. Thus, the native enzyme seems to be dimer of alpha2 type. The pH optima are 4.7 and 5.4 for citrate and (N-morpholino)ethanesulphonic acid buffers, respectively. Adenine and adenosine protect the enzyme against heat inactivation. The enzyme is resistant to -SH reagents, dithiothreitol inhibits it. The Km for adenosine varied from 0.8 to 2.3 micronM depending on temperature and buffer system. The Km for deoxyadenosine was 120 micronM. Besides adenosine, of several nucleosides tested only adenosine N1-oxide, deoxyadenosine and purine riboside acted as substrates. Adenine as well as its derivatives, including plant hormones (cytokinins), have an inhibitory effect on the enzyme. The Ki values of some modified nucleosides and free bases were determined. The physiological role of adenosine nucleosidase in plants is discussed.

Adenosine↗
PubMed1979

[Electron microscopic study of experimental infection. II. A study of the dynamics of Shigella infection].

The dynamics of experimental Shigella infection of chick embryo fibroblasts was studied with the use of electron microscopy. The antibiotic-resistant forms of Sh. sonnei 1,188 was found to be incapable of invasion into the fibroblast cytoplasm and intracellular proliferation. The destruction of fibroblasts observed during the infection was seemingly caused by the action of bacterial endotoxins.

Animals↗
PubMed1976

Studies on the molecular species of DNA polymerase extracted from rat ascites hepatoma cells.

DNA polymerase [EC 2.7.7.7] activities present in hypotonic extract from rat ascites hepatoma AH130 cells were eluted in three separable peaks on DEAE-cellulose column chromatography. Peak I activity had an alkaline pH optimum, and was relatively resistant to SH-blocking reagents and salt concentration. These properties of DEAE peak I are typical of low molecular weight DNA polymerase. DEAE peak II and peak III activities possessed properties corresponding to high molecular weight (6-8 S) polymerase; they showed maximal activity at neutral pH, and were sensitive to SH-blocking reagents and salt. No low molecular weight polymerase activity was released from DEAE peak II or peak III by salt treatment, though partial conversion from DEAE peak II to peak III was observed on the same treatment.

Animals↗
PubMed1979

Studies on lithium transport across the red cell membrane. VI. Properties of a sulfhydryl group involved in ouabain-resistant Na+-Li+ (and Na+-Na+) exchange in human and bovine erythrocytes.

The reactivity of the SH-group essential for ouabain-resistant Na+-Li+ (and Na+-Na+) exchange and its location within the membrane are studied on human and beef erythrocytes and beef red cell ghosts. N-ethylmaleimide (NEM), 1,6-hexane dimaleimide, and iodoacetamide can induce an irreversible, partial inhibition of Na+-Li+ exchange in erythrocytes of the two species. The development of the inhibition due to the alkylating agents is greatly accelerated by external Na+ and Li+. The inhibition takes 3 min (NEM) and 60 min (iodoacetamide) to come to completion in isotonic Na+ media, but is hardly detectable in choline+, K+ or Mg2+ media. The transport site of the exchange system and the site promoting NEM binding exhibit similar affinities for external Na+. The impermeable, monofunctional glutathione derivative of 1,6-hexane dimaleimide does not inhibit Na+-Li+ exchange. The mercurials PCMBS, PCMB, and Hg2+ inhibit Na+-Li+ exchange in beef, but not in human erythrocytes. The inhibitory action of PCMBS, being slightly accelerated by external Na+, is fully reversed by penetrating thiols such as 2-mercaptoethanol, whilst glutathione, an impermeable thiol, is ineffective. Pretreatment with PCMBS affords partial protection from the irreversible inhibition caused by NEM. Oxidation with copper orthophenanthroline inhibits Na+-Li+ exchange only when performed in the presence of penetrating thiols such as 2-mercaptoethanol. It is concluded that the SH-reagents studied inhibit Na+-Li+ exchange by modifying an essential SH-group of a membrane protein in such a way that the turnover number of the exchange system is reduced. This SH-group is separated from both the red cell exterior and interior by a penetration barrier and seems to be distinct from the cation binding site. The action of external Na+ and Li+ in promoting the reaction of alkylating inhibitors is interpreted to result from a conformational change of the transport protein induced by the binding of external Na+ or Li+.

4-Chloromercuribenzenesulfonate↗
PubMed1979

Biochemical alterations of connective tissue metabolism in the arterial walls of stroke-prone spontaneously hypertensive rats.

1. The chemical characteristics of the vascular connective tissue components were determined in stroke-prone (SP), stroke-resistant (SR) spontaneously hypertensive (SH) rats and normotensive Wistar-Kyoto (WK) rats. 2. The ratio of hydroxylysine to hydroxylsine plus lysine in the vascular collagen was increased in 6-month-old SP-SH rats and SR-SH rats as compared with WK rats. 3. An age-related increase in uronic acid and hexose content of the aorta was noted in SP-SH, SR-SH and WK rats. However, the increase was more prominent in SH rats, especially SP-SH rats at the stages examined (11 weeks and over 8 months of age). 4. The ratio of galactosyl-hydroxylysine to glucosyl-galactosyl-hydroxylysine in the aortic collagen was decreased in 6-month-old SH rats, especially SP-SH rats as compared with WK rats. 5. A relative increase in beta and gamma components in aortic collagen was noted in 6-month-old SP-SH rats when compared with SR-SH rats. 6. The increased content of uronic acid and hexose and the structural changes of vascular collagen as demonstrated in SP-SH rats might be related to the fragility of the arterial wall and/or to the pathogenesis of stroke-proneness.

Aging↗
PubMedDate not supplied

[Contribution to the study of some factors affecting semolina quality (author's transl)].

In order to identify certain chemical characteristics of semolina that might provide "a priori" information about its pasta making quality, their relationship to pasta cooking chatacteristics were analyzed. The correlation analysis gave significant values for the relationship between semolina reactive SH content and pasta resistance to disintegration and between urea dispersible protein protein content of semolina and pasta volume increase on cooking. The results obtained suggest that possibility of considering separately the results of the various pasta cooking tests in order to express a conclusive quality evaluation.

Amino Acids↗
PubMedDate not supplied

[Researches on antibiotic-resistance in "Shigella sonnei" and "flexneri" and in "Salmonella typhimurium" (author's transl)].

Ampicillin (A), streptomycin (S), aminosidin (K), chloramphenical (C) and tetracycline (T) resistance was investigated in 130 S. typhi murium, 18 Shigella flexneri and 13 Shigella sonnei strains, recovered from enteritis cases in 1970-1973. All Salmonella and 70% Shigella strains (without any appreciable differences between Sh. sonnei and flexneri) were found resistant and most multiresistant. A-S-K-C-T resistance was frequently found: in 48% of the Salmonella and 12% of the Shigella strains. As for resistance transfer by conjugation, it was obtained in more than 90% of the resistant strains. The Authors, after some remarks about transferable resistance factors diffusion, give some advices on antibiogram making technique.

Anti-Bacterial Agents↗
PubMed1976

Keratinization.

Early studies have already shown that the tonofibrils of malpighian cells consist of a --SH containing fibrous alpha-protein. It was assumed that the highly resistant protective substance, keratin, was formed by the conversion of --SH groups into --S--S--bonds in this protein. This chemical reaction was regarded as the most significant event of the keratinization process. Recent studies show that keratinization proceeds by a synthetic and a degradative stage and that ultimately a complex protective substance is formed. Horny cells become filled with --SH-containing filaments embedded in a --S--S---rich amorphous matrix. This complex is encased by a thickened membrane rendered insoluble by --S--S bonds and an unknown, highly resistant bond. In the stratum corneum, the intercellular space is occupied by bipolar lipids originating from the discharged lamellae of membrane-coating granules.

Animals↗
PubMed1977

Electrophysiology of phagocytic membranes. I. Potassium-dependent slow membrane hyperpolarizations in mice macrophages.

Electrophysiological properties of activated mouse macrophages cultured in vitro were studied using microelectrode techniques. In a high percentage of the individual cells analysed a slow hyperpolarization (SH) was observed with a concomitant decrease (2--4 times) of the input resistance. Increasing doses of tetraethyl ammonium progressively reduce the amplitude of the SH and at a concentration of 15 mM complete blockade of the phenomena is observed. Valinomycin, at a concentration of 10(-7) M produces rapid and permanent hyperpolarization, with a shift in the membrane potential to about --50 mV. These data strongly support the previously proposed hypothesis that the development of SH is due to an increase in the membrane permeability to potassium ions.

Animals↗
PubMed1979

[Membrane proteins of chloroplasts of intact and TMV-infected tobacco plants].

The effects of viral infection on the membrane proteins from tobacco plant chloroplasts differing in their stability for TMV infection were studied. It was shown that the changes in the chloroplasts of labile and resistant tobacco varieties are oppositely directed. The data from amino-acid analysis, SH-group determination and infrared spectra of the membrane proteins of the resistant variety are indicative of conformational changes caused by disruption of the hydrogen bonds, which stabilize the protein, by changes in aggregability, etc. due to infection and metabolic disturbances in the infected cell. The conformational changes in the chloroplasts of the stable variety are adaptive and affect the biological activity, enzymatic and immunological properties and energy metabolism of the chloroplasts.

Amino Acids↗
PubMed1977

Selection from gonococci grown in vitro of a colony type with some virulence properties of organisms adapted in vivo.

Gonococci from subcutaneously implanted chambers in guinea pigs produced, on agar, more than 95% small colonies showing a "double highlight" (DH) effect in oblique reflected light combined with transmitted light. Laboratory strains of gonococci produced some DH colonies, but other showed a single highlight (SH) or no highlight (NH). Selection of DH colonies and comparison of their organisms with gonococci grown in vivo and with those from SH colonies, showed that the DH character was associated with high infectivity for guinea-pig chambers, resistance to killing by human phagocytes and heavy pilation. Furthermore, DH colonies were found in the first culture of three fresh samples of urethral pus. Thus, the DH colony characteristic may be a more reliable criterion of pathogenicity of gonococcal isolates than systems used previously. There were, however, some differences between the gonococci grown in vivo and the DH colony types. The gonococci grown in vivo and cultured once on solid medium possessed one or two antigens which differed from those of DH (or SH) colonies. They also formed smooth suspensions (which separated slowly) in saline, compared with the rough suspensions (which separated quickly) formed by gonococci from DH (or SH) colonies. Finally, the organisms grown in vivo were resistant to killing by human serum whereas the DH (and SH) colony types were susceptible; the resistance of the organisms grown in vivo was lost during one subculture on agar suggesting that the property is a phenotypic characteristic. Hence, in addition to selecting DH colony types the conditions in vivo produce organisms which differ, probably phenotypically, from cultured organisms.

Adaptation, Physiological↗
PubMed1977

Interactions of platinum complexes with the essential and nonessential sulfhydryl groups of thymidylate synthetate.

Thymidylate synthetase (methylenetetrahydrofolate:deoxyuridylate C-methyltransferase) from Lactobacillus casei was progressively inactivated when incubated at 25 degrees C, pH 6.8, in the presence of trans-Pt(NH3)2Cl2. The inhibition appeared to be irreversible, and the rate ofa ctivity loss was dependent on the inhibitor concentration. The corresponding cis isomer was incapable of inhibiting the enzyme under the same conditions. The presence of 2-mercaptoethanol protected the enzyme from inhibition, but did not reactivate enzyme preparations which had been inhibited prior to the addition of the thiol. The interactions of cis- and trans-Pt(NH3)2Cl2 with the enzyme's sulfhydryl (-SH) groups were inferred from the results of spectrophotometric titrations of the enzyme with 5,5'-dithiobis(2-nitrobenzoic acid) and p-hydroxymercuribenzoate. The results suggested that the cis isomer reacted with an average of 1.3 of the enzyme's 4-SH groups and that these were not essential for catalysis. The trans isomer reacted with a total of approximately 2.5 -SH groups, 1.2 of which are essential for catalysis. Neither the trans isomer nor a combination of both isomers was able to react with 1.2 of the 4 -SH groups. Further evidence that the Pt complexes are interacting with enzyme's -SH groups was obtained by reversibly blocking the -SH groups of thymidylate synthetase, and demonstrating the resistance of these preparations to inhibition by the trans Pt complex. Possible explanations for the preferential inhibition of thymidylate synthetase by only one of the two geometric isomers of Pt(NH3)2Cl2 are considered.

Binding Sites↗
PubMed1979

The role of the intrachain disulfide bond in the conformation and stability of the constant fragment of the immunoglobulin light chain.

The conformation and stabilities of the CL fragment isolated from a type lambda Bence Jones protein and the fragment in which the intrachain disulfide bond had been reduced were studied by measuring CD, fluorescence, and ultraviolet absorption. The results indicated that no great conformational change occurs on reduction of the disulfide, unless the SH groups are alkylated. Intact CL was more resistant than reduced CL to guanidine hydrochloride. The denaturation curves were analyzed using an equation based on the binding of guanidine hydrochloride and the free energy changes of denaturation in the absence of the denaturant were estimated as about 6 kcal.mol-1 for intact CL and about 1.8 kcal.mol-1 for reduced CL. The difference in stability between intact CL and reduced CL was explained to a great extent in terms of the entropy change associated with reduction of the intrachain disulfide bond of the fragment in the denatured state.

Bence Jones Protein↗
PubMed1976

A novel chromosome abnormality in human neuroblastoma and antifolate-resistant Chinese hamster cell lives in culture.

Four cell lines, SK-N-SH, SK-N-MC, SK-N-BE(2), and IMR-32, established in vitro from tumor tissue of patients with neuroblastoma were analyzed by trypsin-Giemsa banding methods. In two of the lines a large, abnormally staining chromosome region was observed. This "homogeneously staining region" (HSR) was considerably longer than any of the bands present in normal human cells and, as revealed by both G- and Q-banding, stained with an intermediate intensity. It was located on chromosomes No 6, 10, 17, or 19 of the SK-N-BE(2) cell line and on chromosome No 1 of the IMR-32 line. In concurrent studies, long HSR's were also observed in Chinese hamster sublines that had been exposed to and had developed high levels of resistance to methotrexate or methasquin and high levels of activity of target enzyme dihydrofolate reductase. For several sublines with the highest levels of enzyme activity, approximately 2% of the total cell protein was dihydrofolate reductase. Of 13 independently derived sublines with acquired resistance to antifolate, only those 7 with greater than 100-fold increases in enzyme activity consistently exhibited HSR's. These regions comprised 2-5% of the total length of the chromosome complement and were specifically localized, as demonstrated by G-banding. Analysis of chromosome replication patterns of the HSR in human neuroblastoma and in drug-resistant Chinese hamster cells by tritiated thymidine radioautography indicated that the long, abnormally staining region replicated relatively rapidly and synchronously and terminated replication before the midpoint of the S phase. The HSR thus appeared to represent a novel chromosome abnormality that may be present in cells with specialized functions. Drug-resistant Chinese hamster cells were characterized by overproduction of target enzyme, whereas human neuroblastoma cells had phenotypes of normal neuronal cells. Whether the HSR is transcriptionally active was not elucidated.

Animals↗