ZraP is a periplasmic molecular chaperone and a repressor of the zinc-responsive two-component regulator ZraSR

The bacterial envelope is the interface with the surrounding environment and is consequently subjected to a barrage of noxious agents including a range of compounds with antimicrobial activity. The ESR (envelope stress response) pathways of enteric bacteria are critical for maintenance of the envelope against these antimicrobial agents. In the present study, we demonstrate that the periplasmic protein ZraP contributes to envelope homoeostasis and assign both chaperone and regulatory function to ZraP from Salmonella Typhimurium. The ZraP chaperone mechanism is catalytic and independent of ATP; the chaperone activity is dependent on the presence of zinc, which is shown to be responsible for the stabilization of an oligomeric ZraP complex. Furthermore, ZraP can act to repress the two-component regulatory system ZraSR, which itself is responsive to zinc concentrations. Through structural homology, ZraP is a member of the bacterial CpxP family of periplasmic proteins, which also consists of CpxP and Spy. We demonstrate environmental co-expression of the CpxP family and identify an important role for these proteins in Salmonella's defence against the cationic antimicrobial peptide polymyxin B.     

Eicosanoids and their role in immune modulation in fish—a brief overview

Eicosanoids have been demonstrated to play a central role in immune regulation in mammals brought about by their direct effects on cells such as macrophages and lymphocytes or by their indirect effects via cytokines. Studies have shown that fish mononuclear phagocytes, granulocytes and thrombocytes synthesize and release both cyclooxygenase- and lipoxygenase-derived products such as prostaglandin E₂, leukotriene B₄ and lipoxin A₄. Whether lymphocytes have the ability to generate leukotrienes and lipoxins is still unclear but they do appear to have 12-lipoxygenase activity that leads to the generation of 12-hydroxy fatty acid derivatives. As in mammals, leukotriene and lipoxin biosynthesis requires the presence of a 5-lipoxygenase activating protein-like molecule that is sensitive to the action of the specific inhibitor, MK-886. The prostaglandin-generating ability of trout macrophages can be altered by incubation with lipopolysaccharide suggesting the possible presence of an inducible cyclooxygenase activity. Prostaglandins have been found to suppress the mitogen-induced proliferation of trout leucocytes and the generation of humoral antibody and plasma cells both in vivo and in vitro. The lipoxygenase products, leukotriene B₄ and lipoxin A₄ have more variable effects ranging from inhibition to stimulation depending on the assay system employed. Overall, there is clear evidence that eicosanoids play a role in immune regulation in fish in a similar way to that reported in mammals.     

Effect of REM sleep on retroglossal cross-sectional area and compliance in normal subjects.

It has been proposed that the upper airway compliance should be highest during rapid eye movement (REM) sleep. Evidence suggests that the increased compliance is secondary to an increased retroglossal compliance. To test this hypothesis, we examined the effect of sleep stage on the relationship of retroglossal cross-sectional area (CSA; visualized with a fiber-optic scope) to pharyngeal pressure measured at the level of the oropharynx during eupneic breathing in subjects without significant sleep-disordered breathing. Breaths during REM sleep were divided into phasic (associated with eye movement, PREM) and tonic (not associated with eye movements, TREM). Retroglossal CSA decreased with non-REM (NREM) sleep and decreased further in PREM [wake 156.8 +/- 48.6 mm(2), NREM 104.6 +/- 65.0 mm(2) (P < 0.05 wake vs. NREM), TREM 83.1 +/- 46.4 mm(2) (P = not significant NREM vs. TREM), PREM 73.9 + 39.2 mm(2) (P < 0.05 TREM vs. PREM)]. Retroglossal compliance, defined as the slope of the regression CSA vs. pharyngeal pressure, was the same between all four conditions (wake -0.7 + 2.1 mm(2)/cmH(2)O, NREM 0.6 +/- 3.0 mm(2)/cmH(2)O, TREM -0.2 +/- 3.3 mm(2)/cmH(2)O, PREM -0.6 +/- 5.1 mm(2)/cmH(2)O, P = not significant). We conclude that the intrinsic properties of the airway wall determine retroglossal compliance independent of changes in the neuromuscular activity associated with changes in sleep state.     

Exine and tapetum development in Nymphaea capensis (Nymphaeaceae): a comparative study

The developmental events in microspore envelope and cytoplasm and in tapetum from premeiosis until late tetrad stage were studied in Nymphaea capensis. The exceptional feature of microspore development in this species is that post-meiosis cytokinesis is retarded until the late tetrad stage. Thus, the entire development of the exine becomes completed during the tetrad stage. As a consequence of the retarded cytokinesis, the proximal portion of the forming exine lags behind the distal one during the major part of the tetrad period, but eventually the proximal part of the exine overtakes the distal part in development. The significance of this retardation is discussed. This sequence of events differs sharply from corresponding sporoderm development in other Nymphaea species. Another important topic is the microspore surface activities during exine development. The surface coatings-glycocalyx-are very similar in microspores and in tapetum cells, but their functions are completely different; the roots for this difference are discussed. A noteworthy feature of the developing microspores is the presence of gigantic, deeply cup-like mitochondria; this property is also characteristic of the microspore cytoplasm of N colorata and N. mexicana. A functional significance of these organelles and their adaptive role is discussed.     

Eicosanoid generation in the intertidal barnacle, Balanus perforatus--effect of season and reproductive status

The nature and quantity of the principal lipoxygenase (LO) products generated by the intertidal barnacle Balanus perforatus were examined at monthly intervals and their potential involvement in reproductive events was investigated. The main mono-hydroxy products generated were found to be formed through the action of an 8-lipoxygenase (8-LO) activity and were the mono-hydroxy fatty acids, 8-hydroxyeicosapentaenoic acid (HEPE) and 8-hydroxyeicosatetraenoic acid. Generation of these products was found to be correlated with the environmental seawater temperature, although no change in either 8-LO activity or the precursor fatty acid levels in total phospholipids was found with the time of the year. Changes in fatty acid composition measured in animals collected from summer and winter conditions were found to follow the pattern expected by homeoviscous adaptation of a cold-acclimated animal. Oogenesis was found to occur in August and was linked to a significant reduction in 8-HEPE generation. Spermatozoa were found to be present year-round in the seminal vesicles although the testes became atrophic during the winter months.     

Contamination in HPLC quantified benzaldehyde is from polypropylene microtubes

Semicarbazide-sensitive amine oxidase (SSAO; EC 1.4.3.6) is a copper-containing enzyme predominantly expressed by vascular smooth muscle cells. SSAO deaminates primary amines to produce aldehydes and oxygen peroxides, and may thus play a role in vascular damage. SSAO activity can be quantified by assaying benzaldehyde production using fluorescent derivatisation and separation by HPLC. We performed the derivatisation step in polypropylene or borosilicate glass tubes over 45 min at 95 degrees C. High and obstructing background levels of benzaldehyde were found in one batch of polypropylene vials, as opposed to its alternatives. Treatment and handling of product shipment into the country did not account for introduction of contaminant into packaged vials nor did any reagent used in the assay. We conclude that the source of contamination was most likely due to variation in the commercial production process. Use of borosilicate vials for assays based on aldehyde production and derivatisation is recommended.     

Developmental origins of structural diversity in pollen walls of Compositae

Compositae exhibit some of the most complex and diverse pollen grains in flowering plants. This paper reviews the evolutionary and developmental origins of this diversity in pollen structure using recent models based on the behaviour of colloids and formation of micelles in the differentiating microspore glycocalyx and primexine. The developmental model is consistent with observations of structures recovered by pollen wall dissolution. Pollen wall diversity in Compositae is inferred to result from small changes in the glycocalyx, for example ionic concentration, which trigger the self-assembly of highly diverse structures. Whilst the fine details of exine substructure are, therefore, not under direct genetic control, it is likely that genes establish differences in the glycocalyx which define the conditions for self-assembly. Because the processes described here for Compositae can account for some of the most complex exine structures known, it is likely that they also operate in pollen walls with much simpler organisation.