Structural analysis of Francisella tularensis lipopolysaccharide.

The structure of the lipid A and core region of the lipopolysaccharide (LPS) from Francisella tularensis (ATCC 29684) was analysed using NMR, mass spectrometry and chemical methods. The LPS contains a beta-GlcN-(1-6)-GlcN lipid A backbone, but has a number of unusual structural features; it apparently has no substituent at O-1 of the reducing end GlcN residue in the lipid part in the major part of the population, no substituents at O-3 and O-4 of beta-GlcN, and no substituent at O-4 of the Kdo residue. The largest oligosaccharide, isolated after strong alkaline deacylation of NaBH4 reduced LPS had the following structure: where Delta-GalNA-(1-3)-beta-QuiNAc represents a modified fragment of the O-chain repeating unit. Two shorter oligosaccharides lacking the O-chain fragment were also identified. A minor amount of the disaccharide beta-GlcN-(1-6)-alpha-GlcN-1-P was isolated from the same reaction mixture, indicating the presence of free lipid A, unsubstituted by Kdo and with phosphate at the reducing end. The lipid A, isolated from the products of mild acid hydrolysis, had the structure 2-N-(3-O-acyl4-acyl2)-beta-GlcN-(1-6)-2-N-acyl1-3-O-acyl3-GlcN where acyl1, acyl2 and acyl3 are 3-hydroxyhexadecanoic or 3-hydroxyoctadecanoic acids, acyl4 is tetradecanoic or (minor) hexadecanoic acids. No phosphate substituents were found in this compound. OH-1 of the reducing end glucosamine, and OH-3 and OH-4 of the nonreducing end glucosamine residues were not substituted. LPS of F. tularensis exhibits unusual biological properties, including low endoxicity, which may be related to its unusual lipid A structure.     

THE EFFECTS OF SELECTED INHIBITORS ON CELLULOSE MICROFIBRIL ASSEMBLY IN BOERGESENIA FORBESII (CHLOROPHYTA) PROTOPLASTS1

Protoplasts of Boergesenia forbesii (Harvey) were treated with inhibitors of protein synthesis in order to investigate their effects on cellulose synthesis. Cellulose synthesis was reversibly inhibited by 10 μM cycloheximide as assayed by fluorescence microscopy of Tinopal binding to cellulose. Freeze fracture and image analysis of cycloheximide- treated cells indicated a reduction in the number of intramembrane particles; however, the terminal synthesizing complexes remained at all times. Treatment with 10 μM actinomycin D, when applied during the first hour of protoplast formation, irreversibly inhibits cellulose synthesis and terminal complex formation. De novo protein synthesis is required for cell wall regeneration by protoplasts. The data suggest that the structural subunits visualized in the terminal complex do not undergo significant turnover, but that there may exist an essential proteinaceous component of cellulose synthesis which must be continually renewed.     

Germacra-12,6β-olides from Montanoa revealii and M. mollissima

Montanoa revealii and M. mollissima yielded a series of germacra-12,6β-olides similar to those previously reported from M. hibiscifolia and M. pteropoda.     

Plurality of cyclic nucleotide phosphodiesterase in Spinacea oleracea: subcellular distribution,partial purification,and properties

An active cyclic nucleotide phosphodiesterase has been partially purified from the 100 000 g supernatant of a spinach homogenate. It precipitated at 20–40% saturation with (NH₄)₂SO₄ and was separated on a column of Sephadex G-200 into two major peaks of activity (peaks 1 and 2). Peak 1 (MW 5 × 10⁵) was resolved by column chromatography on DEAE-cellulose into 5 protein fractions; two of these (1_c and 1_m) exhibited cyclic nucleotide phosphodiesterase activity. Subcellular fractionation showed that the phosphodiesterase of highest specific activity is located in the peroxisomes but that an enzyme of relatively high specific activity also occurs in the chloroplast and Golgi fractions. The largest total activity was in the microsomes. Isoelectric focussing of chloroplast phosphodiesterase activity gave two bands corresponding to peaks 1_c and 2. Similar examination of the microsomal, peroxisomal and Golgi fractions showed phosphodiesterases corresponding to peaks 1_m and 2. Peak 1_c activity is greater towards purine 3′,5′-cyclic nucleotides than towards their 2′,3′-isomers; the converse is true of peak 1_m. Examination of the properties of 1_c and 1_m showed a number of other differences. The pH optimum of 1_c is 6.1 and that of 1_m is 4.9. Theophylline (0.1 mM) inhibited 1_c to a greater extent than it did 1_m; Ca²⁺ stimulated 1_c activity but had no effect on 1_m. Pre-incubation with trypsin inhibited 1_m activity whereas similar treatment of 1_c gave an initial 5-fold stimulation. Repeated freezing and thawing of preparations 1_c and 1_m also evoked a difference in response. These results were shown to be attributable to removal of an inhibitor from 1_c. Evidence is presented that an endogenous activator is also present.     

Unifying and distinguishing diversity ordering methods for comparing communities

Diversity indices have been widely used in ecological research, but they remain problematic in that different indices may rank communities inconsistently. This problem can be solved by using diversity ordering methods, the output of which is a diversity profile in graphical form for each community being compared. In this paper, we demonstrate that existing diversity ordering methods can be classified into four groups and that within-group methods are essentially equivalent, while among-group methods are not. We find that the intrinsic diversity-related methods—i.e., the group containing the right tail-sum method, the logarithmic dominance plot, the majorization method, and the k-dominance plot—provide the most stringent test of diversity ordering, and we recommend the right tail-sum method as the method of preference for practical purposes.     

AIRBORNE ALGAE: THEIR PRESENT STATUS AND RELEVANCE1

Ongoing climatic changes coupled with various natural processes and the outcomes of human activities are not only loading the atmosphere with diverse kinds of biological particles but also changing their prevalence and spatial distribution. Despite having considerable ecological and economic significance, including their possible impact on human health, airborne algae are the least‐studied organisms in both aerobiological and phycological studies. The present review has been written to bring together all available information, including a brief survey of the literature, the ecology of airborne algae, mechanisms involved in their aerosolization, the role of environmental factors in shaping the structure and composition of aero‐algal flora, and other significant information associated with airborne algae. This review provides information on methodological approaches and related problems, along with suggestions for areas of future research on airborne algae.     

Autonomic dysreflexia during sperm retrieval in spinal cord injury: influence of lesion level and sildenafil citrate.

Autonomic dysreflexia (AD) can occur during penile vibratory stimulation in men with spinal cord injury, but this is variable, and the association with lesion level is unclear. The purpose of this study was to characterize the cardiovascular responses to penile vibratory stimulation in men with spinal cord injury. We hypothesized that those with cervical injuries would demonstrate a greater degree of AD compared with men with thoracic injuries. We also questioned whether the rise in blood pressure could be attenuated by sildenafil citrate. Participants were classified as having cervical (n = 8) or thoracic (n = 5) injuries. While in a supine position, subjects were instrumented with an ECG, and arterial blood pressure was determined beat by beat. Subjects reported to the laboratory twice and received an oral dose of sildenafil citrate (25-100 mg) or no medication. Penile vibratory stimulation was performed using a handheld vibrator to the point of ejaculation. At ejaculation during the nonmedicated trials, the cervical group had a significant decrease in heart rate (-5-10 beats/min) and increase in mean arterial blood pressure (+70-90 mmHg) relative to resting conditions, whereas the thoracic group had significant increases in both heart rate (+8-15 beats/min) and mean arterial pressure (+25-30 mmHg). Sildenafil citrate had no effect on the change in heart rate or mean arterial pressure in either group. In summary, men with cervical injuries had more pronounced AD during penile vibratory stimulation than men with thoracic injuries. Administration of sildenafil citrate had no effect on heart rate or blood pressure during penile vibratory stimulation in men with spinal cord injury.