Protein A of quinolinate synthetase is the site of oxygen poisoning of pyridine nucleotide coenzyme synthesis in Escherichia coli.

De novo biosynthesis of pyridine nucleotide coenzymes in Escherichia coli is initiated by an enzyme complex (quinolinate synthetase) containing protein B which converts -aspartate into iminoaspartate protein A, which then generates quinolinate on the pathway to the coenzymes. This complex has been shown to be poisoned by hyperbaric oxygen. ^7,8 We performed assays made dependent on both proteins B and A versus only protein A, using cell-free extracts of hyperbaric-oxygen poisoned and aerobically grown cells. The specific activities were produced by a similar amounts of 68% and 60%, respectively, when measured in assays made dependent on enzymes B and A versus only protein A that was derived from oxygen-poisoned extract. Thus, protein A is the oxygen-sensitive component.     

Peroxidase activity in non-embryogenic and embryogenic calli and in developing somatic embryos of white fir (Abies concolor Gord. et Glend)

ABSTRACT

Peroxidase activity was monitored during somatic embryogenesis of white fir (Abies concolor Gord. et Glend) starting from a non-embryogenic callus. Results revealed profound differences between non-embryogenic and embryogenic calli with an elevated level of enzyme activity in non-embryogenic ones. Precotyledonary, early cotyledonary and late cotyledonary stages of somatic embryogenesis were characterized by a substantially reduced peroxidase activity compared to callus tissues and regenerated plantlets. Changes in peroxidase activity are as a rule paralleled by variation in isoenzyme composition. The utility of the enzyme in the induction stage of somatic embryogenesis in white fir is proposed.     

Soluble tumour necrosis factor-α receptor type 1 as a biomarker of response to phototherapy in patients with psoriasis

Abstract

The purpose of the study was to analyze the relationship between the serum concentration of soluble tumour necrosis factor-α type 1 (sTNF-R1), the severity of plaque-type psoriasis and therapeutic response. We compared sTNF-R1 in 25 patients treated with narrowband ultraviolet B (NB-UVB) radiation and 25 patients treated with systemic photochemotherapy (psoralen plus UVA – PUVA). The pretreatment Psoriasis Area and Severity Index (PASI) score and sTNF-R1 concentration were 16.32±5.26 and 1.99±0.40 ng ml^?1, respectively, in the group treated with NB-UVB, and 17.22±3.48 and 2.07±0.31 ng ml^?1, respectively, in the group treated with PUVA. The concentration of sTNF-R1 in healthy controls was 1.49±0.34 ng ml^?1 (p<0.05 compared with patients with psoriasis). The pretreatment PASI score correlated with sTNF-R1 in both treatment groups (r=0.46 and r=0.44, p<0.05). NB-UVB and PUVA gave similar therapeutic effects (the PASI score after 20 treatments was 4.42±1.67 in the NB-UVB-treated group and 5.55±2.10 in PUVA-treated patients); however, the sTNF-R1 concentration at the same time differed significantly: 1.52±0.37 ng ml^?1 and 1.98±0.39 ng ml^?1 (p<0.001), respectively. Moreover, the decline in sTNF-R1 in both treatment groups was significant only in patients in whom the duration of skin lesions was less than 3 months. The results suggest that the value of serum sTNF-R1 concentration as a marker of response to phototherapy may depend on duration of skin lesions and the treatment method.     

Convergent Antibody Signatures in Human Dengue

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An immunoblotting as a method for the diagnosis of typhoid fever

The patients' sera had been referred to the National Salmonella Centre for routine Widal serology. Sera were predominately from patients suspected of having been infected with Salmonella Typhi, but also included one serum from patient with typhoid fever who was culture positive for Salmonella Typhi. The immunoblotting procedure using Salmonella Typhi somatic (O=9,12 LPS) and flagellar (H=d) antigens was used for preliminary testing of selected patients sera previously evaluated by Widal agglutination assay as containing different levels of antibodies against O and/or H antigens of Salmonella Typhi. Following Chart et al., immunoblotting reactions were graded between 0 and 3, with 0 indicating an absence of antibody binding, and 3 where antibody binding was readily observed. Sera giving reaction of 2 or 3 were considered to be antibody positive for this study. Positive immunoblotting reaction to O=9,12 LPS antigen was obtained only with the serum of patient with typhoid fever. Presence of specific anti-LPS antibodies was also observed in two other patients' sera diluted 1:50, and in case of one of them also in dilution 1:200, but intensity of antigen-antibody reaction was under positive result criterion. The most other sera positive to O=9,12 antigen in law dilutions (1:50, 1:100) by Widal assay, showed the traces of non-specific reaction by immunoblotting. Presence of positive antigen-antibody reaction was indicated for five sera in dilution 1:50 when tested with the >55 kDa H=d flagellar protein subunit, including the serum of patient with typhoid fever. Only in this serum the high level of specific antibodies was detected also in dilution 1:200, what was not observed in case of the other four, which appeared negative. All the other sera were shown not to contain antibodies to flagella antigen. Although the presented results are preliminary and additional study of more sera of people infected with Salmonella Typhi is needed, it can be concluded after Chart et al., that an immunoblotting procedure incorporating O=9,12 LPS and flagellar H=d antigens is a useful method for providing serological evidence of infection with Salmonella Typhi. In our opinion it can serve as a rapid test for the diagnosis of typhoid fever.     

Selective cortical interneuron and GABA deficits in cyclin D2-null mice

In contrast to cyclin D1 nulls (cD1-/-), mice without cyclin D2 (cD2-/-) lack cerebellar stellate interneurons; the reason for this is unknown. In the present study in cortex, we found a disproportionate loss of parvalbumin (PV) interneurons in cD2-/- mice. This selective reduction in PV subtypes was associated with reduced frequency of GABA-mediated inhibitory postsynaptic currents in pyramidal neurons, as measured by voltage-clamp recordings, and increased cortical sharp activity in the EEGs of awake-behaving cD2-/- mice. Cell cycle regulation was examined in the medial ganglionic eminence (MGE), the major source of PV interneurons in mouse brain, and differences between cD2-/- and cD1-/- suggested that cD2 promotes subventricular zone (SVZ) divisions, exerting a stronger inhibitory influence on the p27 Cdk-inhibitor (Cdkn1b) to delay cell cycle exit of progenitors. We propose that cD2 promotes transit-amplifying divisions in the SVZ and that these ensure proper output of at least a subset of PV interneurons.     

Modification of membranes by quercetin, a naturally occurring flavonoid, via its incorporation in the polar head group

Quercetin is a naturally occurring flavonoid that has a lot of beneficial properties to human health. In this report, using the spin label technique, the influence of quercetin on the fluidity of multilamellar DPPC liposomes was studied. The polarity of the environment preferred by quercetin was also examined by determining the dependence of the position of electronic absorption maxima on dielectric properties of different environments. Autofluorescence of quercetin was also used to examine its distribution in cells. An additional aim of the study was to find how quercetin presence affects human skin fibroblasts. The results showed that incorporation of quercetin at physiological pH into DPPC liposomes caused changes in the partition coefficient of the Tempo spin label between water and polar head group phases. By determining the electronic absorption maxima, we observed that the chromophore of quercetin is localized in the polar head region. Fluorescence microscopy of HSF cells showed quercetin presence in the membrane, cytoplasm and inside the nucleus. Ultrastructural observation revealed some changes, especially in membranous structures, after flavonol treatment. From the results we have concluded that quercetin present in the membrane and other structures can cause changes within cells crucial for its pharmacological activity.