Suppression of growth defects of α-amylase secreting Escherichia coli by signal sequence fusion

Abstract In a previous study, we have described unusual cross-reactions among monoclonal antibodies (Mabs) to bacteria and in particular to the Inaba and Ogawa serotypes of Vibrio cholerae . In this study, the extent to which the binding sites of both antibodies and antigens overlap has been investigated by competitive binding and idiotypic analysis. The competitive binding data indicate that the cross-reactive binding of the Inaba Mabs to the Ogawa vibrios can be abolished by incubation with higher affinity Ogawa Mabs. However, rabbit antiserum raised against the Inaba series does not react with the Ogawa series, indicating that anti-Inaba Mabs do not share idiotypic determinants with anti-Ogawa Mabs. The results therefore suggest that the two sets of antibodies recognise different determinants which are closely related in spatial terms, and which consequently do not permit simultaneous binding of the two types of monoclonal antibody.     

Transduction of envelope stress in Escherichia coli by the Cpx two-component system.

Disruption of normal protein trafficking in the Escherichia coli cell envelope (inner membrane, periplasm, outer membrane) can activate two parallel, but distinct, signal transduction pathways. This activation stimulates the expression of a number of genes whose products function to fold or degrade the mislocalized proteins. One of these signal transduction pathways is a two-component regulatory system comprised of the histidine kinase CpxA and the response regulator, CpxR. In this study we characterized gain-of-function Cpx* mutants in order to learn more about Cpx signal transduction. Sequencing demonstrated that the cpx* mutations cluster in either the periplasmic, the transmembrane, or the H-box domain of CpxA. Intriguingly, most of the periplasmic cpx* gain-of-function mutations cluster in the central region of this domain, and one encodes a deletion of 32 amino acids. Strains harboring these mutations are rendered insensitive to a normally activating signal. In vivo and in vitro characterization of maltose-binding-protein fusions between the wild-type CpxA and a representative cpx* mutant, CpxA101, showed that the mutant CpxA is altered in phosphotransfer reactions with CpxR. Specifically, while both CpxA and CpxA101 function as autokinases and CpxR kinases, CpxA101 is devoid of a CpxR-P phosphatase activity normally present in the wild-type protein. Taken together, the data support a model for Cpx-mediated signal transduction in which the kinase/phosphatase ratio is elevated by stress. Further, the sequence and phenotypes of periplasmic cpx* mutations suggest that interactions with a periplasmic signaling molecule may normally dictate a decreased kinase/phosphatase ratio under nonstress conditions.     

Aluminium causes nutrient imbalance and structural changes in the needles of Scots pine without inducing clear root injuries

The effects of aluminium chloride (AICI3) treatments (50 and 150 mg/l) on 3-year-old Scots pine (Pinus sylvestris L.) seedlings were studied in a sand culture during 2 growing periods in an open field experiment. Even by the end of the first growing period, a decline was observed in the concentrations of Ca, Mg and P within the needles, and of Ca and Mg in the roots. After the second growing period, increased N and K concentrations were observed in the needles of Al-treated seedlings. Both the needles and roots of Al-treated seedlings showed, after the second growing period, a decline in growth and increased concentrations of AI as the amount of AICI3 in the nutrient solution increased. Al-induced changes in needle structure were found to be symptomatic of a nutrient imbalance, particularly of Mg and P. Al-stress did not result in any observable changes in root anatomy or in the number of mycorrhizas. Scots pine proved to be rather resistant to Al-stress, indicating that direct Al-injuries are not likely in the field, though Al-stress may be a contributing factor in the formation of nutrient imbalances.     

Chemical composition and ultrastructural changes in Scots pine needles in a forest decline area in southwestern Finland

Tree decline and deaths have been observed among 15 to 20-year-old Scots pines (Pinus sylvestris L.) in a dry heath forest in southwestern Finland. The sudden decline in height growth, the dieback of leading shoots and the yellowing of needles in young shoots in the upper part of the tree are typical symptoms of the decline of these young pines. Needle ultrastructure and chemical composition of Scots pines with or without decline and fluctuations of them in different seasons were studied. Afflicted trees were found to suffer from a deficiency in calcium and magnesium with low concentration of foliar nitrogen and phosphorus observed in all the trees studied. Ultrastructural study revealed changes characteristic of different seasons and measured nutrient status of needles. A clear reduction of membrane system in chloroplasts, especially related to Mg deficiency, was observed in most samples. The symptoms related to N deficiency, the translucent appearance of the cytoplasm and chloroplast stroma, and the elongated chloroplasts, as well as swelling of mitochondria, indicating P deficiency, were also found in the needles sampled from this forest decline area. The present study showed that it is possible to detect specific nutrient deficiency symptoms in needle ultrastructure in field samples and for use as sensitive indicators of unbalanced nutrient status.     

Increased urinary excretion of free N-acetylneuraminic acid in thirteen patients with Salla disease

Thirteen severely retarded patients with Salla disease, a new type of lysosomal storage disorder, have been studied biochemically. All patients excreted approximately ten times more free sialic acid than normal individuals. The isolated sialic acid was characterized by paper chromatography, thin-layer chromatography, optical rotation, 13C and 1H nuclear magnetic resonance spectroscopy, and mass spectrometry of its permethylated derivative. The results clearly indicated that the excreted sialic acid was identical to N-acetylneuraminic acid. The main sialylated trisaccharide present in the urine of the patients was identified as 3'-sialyllactose by sugar and methylation analysis. The excreted amounts were found to be within normal range.     

Whether to have a second child or not? An integrative approach to women's reproductive decision-making in current China

The transition to low fertility worldwide has led to introduction of diverse frameworks across disciplines to understand its causes and consequences. Previous attempts to compare the relative importance of the key factors influencing women's fertility decision-making largely focused on a single rather than multiple steps of decision-making—an important problem if different factors are associated with different steps. Furthermore, insufficient attention has been paid explicitly to husband's and already-born children's influences, two potentially important factors. Here we introduce a framework covering three steps of reproductive decision-making—ideal family size, fertility desire and fertility intention—and test it using multi-level survey data collected from Chinese one-child mothers. Mother's attitudes towards having two children were paramount factors underlying her ideal family size, and husband's and the firstborn child's attitudes were critical to her desire to have a second child, which in turn played a decisive role in her intention to have a second child. Although husband's attitude was related to all steps, most factors were only relevant to one step; e.g., perceived child mortality and value for old-age security predicted ideal family size, admiration—a prerequisite for social learning—for two-child families predicted fertility desire, and physical/economic constraints primarily predicted fertility intention. Our study emphasizes multiple decision-makers in family reproduction; indicates the relative importance of fertility-influencing factors could vary with steps of decision-making; and has important implications for population policy in low-fertility societies.     

Regulation of surfactant proteins by LPS and proinflammatory cytokines in fetal and newborn lung

Intra-amniotic lipopolysaccharide (LPS) and cytokines may decrease respiratory distress syndrome (RDS) and increase chronic lung disease in the newborn. The aim was to identify the primary inflammatory mediators regulating the expression of surfactant proteins (SP) in explants from immature (22-day-old fetus) and mature (30-day term fetus and 2-day-old newborn) rabbits. In immature lung, interleukin (IL)-1alpha and IL-1beta upregulated the expression of SP-A and SP-B. These effects of IL-1 were diminished, and SP-C mRNA was suppressed additively in the presence of tumor necrosis factor (TNF)-alpha and either LPS or interferon (IFN)-gamma. LPS, TNF-alpha, or IFN-gamma had no effect alone. In explants from the term fetus and the newborn, LPS, IL-1alpha, and TNF-alpha additively suppressed the SPs. LPS acutely induced IL-1alpha in alveolar macrophages in mature lung but not in the immature lung. IFN-gamma that generally has low expression in intrauterine infection decreased the age dependence of the other agonists' effects on SPs. The present study serves to explain the variation of the pulmonary outcome after an inflammatory insult. We propose that IL-1 from extrapulmonary sources induces the SPs in premature lung and is responsible for the decreased risk of RDS in intra-amniotic infection.     

Depletion of the photosystem II core complex in mature tobacco leaves infected by the flavum strain of tobacco mosaic virus

The flavum strain of Tobacco mosaic virus (TMV) differs from the wild-type (wt) virus by causing strong yellow and green mosaic in the systemically infected developing leaves, yellowing in the fully expanded leaves, and distinct malformations of chloroplasts in both types of infected tissues. Analysis of the thylakoid proteins of flavum strain-infected tobacco leaves indicated that the chlorosis in mature leaves was accompanied by depletion of the entire photosystem II (PSII) core complexes and the 33-kDa protein of the oxygen evolving complex. The only change observed in the thylakoid proteins of the corresponding wt TMV-infected leaves was a slight reduction of the alpha and beta subunits of the ATP synthase complex. The coat proteins of different yellowing strains of TMV are known to effectively accumulate inside chloroplasts, but in this work, the viral movement protein also was detected in association with the thylakoid membranes of flavum strain-infected leaves. The mRNAs of different enzymes involved in the chlorophyll biosynthesis pathway were not reduced in the mature chlorotic leaves. These results suggest that the chlorosis was not caused by reduction of pigment biosynthesis, but rather, by reduction of specific proteins of the PSII core complexes and by consequent break-down of the pigments.