Biophysical properties of membrane lipids of anammox bacteria:I. Ladderane phospholipids form highly organized fluid membranes

AbstractAnammox bacteria that are capable of anaerobically oxidizing ammonium (anammox) with nitrite to nitrogen gas produce unique membrane phospholipids that comprise hydrocarbon chains with three or five linearly condensed cyclobutane rings. To gain insight into the biophysical properties of these ‘ladderane’ lipids, we have isolated a ladderane phosphatidylcholine and a mixed ladderane phosphatidylethanolamine/phosphatidylglycerol lipid fraction and reconstituted these lipids in different membrane environments. Langmuir monolayer experiments demonstrated that the purified ladderane phospholipids form fluid films with a relatively high lipid packing density. Fluid-like behavior was also observed for ladderane lipids in bilayer systems as monitored by cryo-electron microscopy on large unilamellar vesicles (LUVs) and epi-fluorescence microscopy on giant unilamellar vesicles (GUVs). Analysis of the LUVs by fluorescence depolarization revealed a relatively high acyl chain ordering in the hydrophobic region of the ladderane phospholipids. Micropipette aspiration experiments were applied to study the mechanical properties of ladderane containing lipid bilayers and showed a relatively high apparent area compressibility modulus for ladderane containing GUVs, thereby confirming the fluid and acyl chain ordered characteristics of these lipids. The biophysical findings in this study support the previous postulation that dense membranes in anammox cells protect these microbes against the highly toxic and volatile anammox metabolites

Reliability and Reproducibility of the OTA/AO Classification for Humeral Shaft Fractures

Objectives: This study aimed to determine interobserver reliability and intraobserver reproducibility of the OTA/AO classification for humeral shaft fractures, and to evaluate differences between fracture types, fracture groups, and surgical specializations. Methods: Thirty observers (25 orthopaedic trauma surgeons and 5 general orthopaedic surgeons) independently classified 90 humeral shaft fractures according to the OTA/AO classification. Patients of 16 years and older were included. Periprosthetic, recurrent, and pathological fractures were excluded. Radiographs were provided in random order, and observers were blinded to clinical information. To determine intraobserver agreement, radiographs were reviewed again after 2 months in a different random order. Agreement was assessed using kappa statistics. Results: Interobserver agreement for the 3 fracture types was moderate (κ = 0.60; 0.59-0.61). It was substantial for type A (κ = 0.77; 0.70-0.84) and moderate for type B (κ = 0.52; 0.46-0.58) and type C fractures (κ = 0.46; 0.42-0.50). Interobserver agreement for the 9 fracture groups was moderate (κ = 0.48; 95% CI, 0.48-0.48). Orthopaedic trauma surgeons had better overall agreement for fracture types, and general orthopaedic surgeons had better overall agreement for fracture groups. Observers classified 64% of fractures identically in both rounds. Intraobserver agreement was substantial for the 3 types (κ = 0.80; 0.77-0.81) and 9 groups (κ = 0.80; 0.77-0.82). Intraobserver agreement showed no differences between surgical disciplines. Conclusions: The OTA/AO classification for humeral shaft fractures has a moderate interobserver and substantial intraobserver agreement for fracture types and groups

Towards a new approach for the design of the alignment of highways and railroads

Thesis (M. Ing.) -- University of Stellenbosch, 1998.Full text to be digitised and attached to bibliographic record

Towards the extension of the knowledgebase to further the understanding and modelling of driver behaviour

Thesis (PhD)--University of Stellenbosch, 2003.ENGLISH ABSTRACT: The problem of how the mind relates to the brain stands as one of the greatest challenges today. The materialistic worldview and pragmatic approach to social problems are both being transformed by discoveries of how human experience and culture arise in cerebral activity. Even so, this effort, spearheaded by neuroscience, has seen the important and contentious issue of driver behaviour somehow been left behind. From an extensive literature study, it can be concluded that gross disregard of the neural underpinnings of such behaviour tied to a behaviouristic approach is endemic to the field. Numerous qualitative psychological models (each associated with debates about their validity) and Artificial Intelligence models, which effectively only imitate robots 'impaired' to display some humanlike characteristics, were come across. Although neural networks are derived from current knowledge of computation within the brain and deployed in industry, human driver behaviour modelling is not benefiting from this revolution in humanlike information processing. To date, very little has been done to determine what makes road users speed, drive while drunk, overtake, or yield at crossroads. As the central nervous system is the human measuring device in and of the world and thus key affector of human behaviour, it is ofutrnost importance to invest resources in 'inoculating' the field of driver behaviour modelling onto a robust basis provided by neuroscience. Being a human driver incorporates a broad complement of interrelated brain systems to perform driving tasks (psychological functions) at hand, such as lane keeping, speed choice, risk perception, and obstacle avoidance. The proper level of analysis of such a psychological function is the level at which that function is represented in the brain. Providing a theoretical model of human behaviour, based on biological facts of the brain as a whole, is surely a challenge for decades to come, but the field of driver behaviour should be part of such an effort. Collaboration is needed among investigators from the fields of neuroscience, psychology, mathematics, computer science, and engineering to further driver behaviour modelling. It is uncommon that professionals from these fields have a thorough understanding of the other fields involved, but the author, not pretending to be an expert, argues that such a union of fields will be of significant value not only to transportation, but all behavioural sciences. The wealth of to-date knowledge amassed in neuroscience lies ready to be tapped by researchers interested in explaining human driver behaviour. To this end, the use of modem brain-imaging techniques will be invaluable in pinning down the neural correlates of particular driving subtasks, bearing in mind the extent of structural impacts on the brain of each individual, brought about by a lifetime of interaction with the environment. Thus, based on the findings of this literature study, the author proposes that supplementary work be conducted by a multi-disciplinary team to roll-out an experiment to study the nature of environmental stimuli as instigators of aggression and road rage, by drawing on knowledge about brain imaging and (amygdala) activation.AFRIKAANSE OPSOMMING: Die vraagstuk hoe die verstand [denke] met die brein in verband staan, is een van die grootste uitdagings tans. Die materialistiese wêreldbeskouing sowel as die pragmatiese benadering van maatskaplike probleme word verander deur ontdekkings aangaande die wyse waarop menslike ervaring en kultuur hul in serebrale aktiwiteit voordoen. Desondanks is in hierdie poging, met die neurowetenskap aan die spits, die belangrike en omstrede kwessie van bestuurdersgedrag om een of ander rede agterweë gelaat. Uit 'n uitgebreide literatuurstudie kan afgelei word dat grootskaalse verontagsaming van die neurale basis van sodanige gedrag gekoppel aan 'n behavioristiese benadering endemies is aan die gebied. Talle kwalitatiewe sielkundige modelle en kunsmatige intelligensiemodelle is teëgekom, elk gepaard met debatte oor die geldigheid daarvan. Hoewel neurale netwerkmodelle gebaseer word op huidige kennis van verwerking binne die brein en ontplooi word in die industrie, trek menslike bestuurdersgedragmodellering nie voordeel uit hierdie revolusie in neurale inligtingsverwerking nie. Tot op hede is baie min gedoen om vas te stel waarom padgebruikers jaag, dronkbestuur, verbysteek of by kruispaaie toegee. Aangesien die sentrale senuweestelsel die menslike meettoestel in en van die wêreld is en dus die sleutelbeïnvloeder van menslike gedrag is, is dit van die uiterste belang om middele te investeer in die fundering van die gebied van bestuurdersgedragmodellering op 'n stewige basis daargestel deur die neurowetenskappe. Om'n menslike bestuurder te wees behels 'n omvattende komplement van verbandhoudende breinstelsels om bestuurstake (sielkundige funksies) te verrig, soos spoedkeuse, risikowaarneming en die vermyding van obstruksies. Die gepaste ontledingsvlak van so 'n sielkundige funksie is die vlak waarop daardie funksie in die brein verteenwoordig word. Die daarstelling van 'n teoretiese model van menslike gedrag, gebaseer op biologiese feite van die brein in die geheel, is gewis nog vir komende dekades 'n uitdaging, maar die gebied van bestuurdersgedrag moet deel uitmaak van so 'n pogmg. Samewerking is nodig tussen navorsers uit die neurowetenskappe, sielkunde, wiskunde, rekenaarwetenskap en ingenieurswese om bestuurdersgedragmodellering te bevorder. Dit is ongewoon dat vakkundiges uit hierdie velde 'n deeglike begrip het van die ander gebiede wat betrokke is, maar die outeur, sonder om voor te gee dat hy 'n deskundige is, betoog dat so 'n samesnoering van vakgebiede van betekenisvolle waarde sal wees, nie net vir die vervoerwese nie, maar ook vir al die gedragwetenskappe. Die omvang van die jongste kennis wat in die neurowetenskappe vergaar is, lê gereed om deur navorsers benut te word wat belang stel in die verklaring van menslike bestuurdersgedrag. Met dié doel sal die gebruik van moderne breinskanderingstegnieke van onskatbare waarde wees om die neurale korrelate van bepaalde bestuursubtake vas te pen, gedagtig aan die omvang van strukturele impakte op die brein van elke indiwidu teweeggebring deur 'n leeftyd van interaksie met die omgewing. Daarom, gebaseer op die bevindinge van hierdie literatuurstudie, stel die outeur voor dat addisionele werk gedoen word deur 'n multi-dissiplinêre span ten einde 'n eksperiment uit te voer, waarin die aard van stimuli uit die omgewing, wat lei tot padwoede, bestudeer kan word, met inagneming van die beskikbare kennis oor breinskandering en (amygdala) -aktiveringpatrone

Smartphone Tests of Visual Acuity, Hyper-acuity, Contrast Sensitivity and Critical Flicker Fusion

Testing of the afferent visual system within the confines of smartphone hardware limitations would make assessment of visual acuity, contrast sensitivity, and critical flicker fusion available in a wide variety of settings, such as in the emergency department, in outpatient clinics, or in the home. Reliable smartphone-based testing could improve triage, as well as allow patients with known disease to monitor their vision at home frequently, if needed

Phosphorylation and Functional Properties of the IIA Domain of the Lactose Transport Protein of Streptococcus thermophilus

The lactose-H(+) symport protein (LacS) of Streptococcus thermophilus has a carboxyl-terminal regulatory domain (IIA(LacS)) that is homologous to a family of proteins and protein domains of the phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS) in various organisms, of which IIA(Glc) of Escherichia coli is the best-characterized member. On the basis of these similarities, it was anticipated that IIA(LacS) would be able to perform one or more functions associated with IIA(Glc), i.e., carry out phosphoryl transfer and/or affect other catabolic functions. The gene fragment encoding IIA(LacS) was overexpressed in Escherichia coli, and the protein was purified in two steps by metal affinity and anion-exchange chromatography. IIA(LacS) was unable to restore glucose uptake in a IIA(Glc)-deficient strain, which is consistent with a very low rate of phosphorylation of IIA(LacS) by phosphorylated HPr (HPr∼P) from E. coli. With HPr∼P from S. thermophilus, the rate was more than 10-fold higher, but the rate constants for the phosphorylation of IIA(LacS) (k(1) = 4.3 × 10(2) M(−1) s(−1)) and dephosphorylation of IIA(LacS)∼P by HPr (k(−1) = 1.1 × 10(3) M(−1) s(−1)) are still at least 4 orders of magnitude lower than for the phosphoryltransfer between IIA(Glc) and HPr from E. coli. This finding suggests that IIA(LacS) has evolved into a protein domain whose main function is not to transfer phosphoryl groups rapidly. On the basis of sequence alignment of IIA proteins with and without putative phosphoryl transfer functions and the known structure of IIA(Glc), we constructed a double mutant [IIA(LacS)(I548E/G556D)] that was predicted to have increased phosphoryl transfer activity. Indeed, the phosphorylation rate of IIA(LacS)(I548E/G556D) by HPr∼P increased (k(1) = 4.0 × 10(3) M(−1) s(−1)) and became nearly independent of the source of HPr∼P (S. thermophilus, Bacillus subtilis, or E. coli). The increased phosphoryl transfer rate of IIA(LacS)(I548E/G556D) was insufficient to complement IIA(Glc) in PTS-mediated glucose transport in E. coli. Both IIA(LacS) and IIA(LacS)(I548E/G556D) could replace IIA(Glc), but in another function: they inhibited glycerol kinase (inducer exclusion) when present in the unphosphorylated form