The Xerobranching Response Represses Lateral Root Formation When Roots Are Not in Contact with Water

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Immunity in human schistosomiasis mansoni: cross-reactive IgM and IgG2 anti-carbohydrate antibodies block the expression of immunity

We have previously reported that the slow development of immunity to reinfection after treatment of Schistosoma mansoni infections is partly attributable to the continued presence of 'blocking' antibodies in young, susceptible children. A further analysis of this phenomenon supports the hypothesis that such blocking antibodies can be of the IgG2 as well as the IgM isotype, and that they react with carbohydrate epitopes expressed both on egg polysaccharides and on schistosomulum surface antigens, of particular importance being those antigens that are shed from the schistosomulum surface during the early stages of maturation in vitro. Evidence is also presented that, in those patients lacking high levels of IgG2 blocking antibodies, resistance to reinfection after treatment is associated with the presence of other IgG isotypes against the same shed antigens.     

An investigation of the interactions of some factors influencing the infectivity of Schistosoma mansoni miracidia to Biomphalaria glabrata

Sturrock R. F. and Upatham E. S. 1973. An investigation of the interactions of some factors influencing the infectivity of Schistosoma mansoni miracidia to Biomphalaria glabrata. International Journal for Parasitology3: 35–41. A 3³ replicated factorial experiment showed that there were significant first-order interactions between the effects of turbidity, salinity and pH on the infectivity of Schistosoma mansoni miracidia to Biomphalaria glabrata. The main factor effects resembled those obtained when the factors were studied individually. There was a negative regression of infection rate on the logarithm of the level of both turbidity and salinity, and a curvilinear regression on pH, with a peak between 7 and 8. However, as the main factors only accounted for little over half of the observed variance, the interactions are extremely important and greatly reduce the chance of a miracidium infecting a snail. These findings are relevant to natural transmission sites in endemic areas and also suggest that quite minor variations in other factors may enhance the adverse effect of increased salinity on transmission in estuaries, and thus minimize the importance of such areas in the epidemiology of the parasite.     

Enhancement by caffeine of N-methyl-N-nitrosourea-induced mutations and chromosome aberrations in Chinese hamster cells

N-Methyl-N-nitrosourea (MNU) increased the induction of mutations to 8-azaguanine resistance in Chinese hamster cells in a dose-dependent manner. Mutations were only observed with toxic concentrations of MNU. Since a plot of the fraction of cells surviving alkylation against the extent of methylation of DNA exhibited a shoulder it followed that there was a threshold level of DNA reaction which did not lead to mutations possibly due to efficient repair of DNA damage. Post-alkylation incubation in medium containing caffeine decreased cell survival while at the same time it increased the induced mutation frequency. Mutation frequency was increased whether caffeine was present for 48 h or for a further 12 days in the presence of the selective agent 8-azaguanine. MNU caused chromatid aberrations in Chinese hamster cells and these reached a value of 15% of the treated cells by 48 h after methylation. Post-alkylation incubation in caffeine increased the percentage of cells showing chromosomal damage to a maximum of 86% of treated cells by 40 h after alkylation. A large proportion of cells exhibited completely fragmented or shattered chromosomes. The proportion of cells showing the presence of micronuclei also dramatically increased following incubation of methylated cells in caffeine. These results are discussed in terms of the possibility that damage to DNA is responsible for the lethal, mutagenic and cytological effects of MNU in Chinese hamster cells, and that there is a caffeine sensitive step(s) in the repair of the DNA damage which is responsible for these effects.     

The use of zootherapeutics in folk veterinary medicine in the district of Cubati, Paraíba State, Brazil

Background

Viewed through the micro focus of an interpretive lens, medical anthropology remains mystified because interpretivist explanations seriously downplay the given context in which individual health seeking-behaviours occur. This paper draws upon both the interpretivist and political economy perspectives to reflect on the ethno medical practices within the Korean-Australian community in Sydney.

Methods

We draw on research data collected between 1995 and 1997 for an earlier study of the use of biomedical and traditional medicine by Korean-Australians in Sydney. A total of 120 interviews were conducted with a range of participants, including biomedical doctors, traditional health professionals, Korean community leaders and Korean migrants representing a range of socio-economic backgrounds and migration patterns.

Results and Discussion

First, the paper highlights the extent to which the social location of migrants in a host society alters or restructures their initial cultural practices they bring with them. Second, taking hanbang medicine in the Korean-Australian community as an illustrative case, the paper explores the transformation of the dominant biomedicine in Australia as a result of the influx of ethnomedicine in the era of global capitalism and global movement.

Conclusion

In seeking to explain the popularity and supply of alternative health care, it is important to go beyond the culture of each kind of health care itself and to take into consideration the changes occurring at societal, national and global levels as well as consequential individual response to the changes. New social conditions influence the choice of health care methods, including herbal/alternative medicine, health foods and what are often called New Age therapies.     

Crystal structure of protoporphyrinogen oxidase from Myxococcus xanthus and its complex with the inhibitor acifluorfen

Protoporphyrinogen IX oxidase, a monotopic membrane protein, which catalyzes the oxidation of protoporphyrinogen IX to protoporphyrin IX in the heme/chlorophyll biosynthetic pathway, is distributed widely throughout nature. Here we present the structure of protoporphyrinogen IX oxidase from Myxococcus xanthus, an enzyme with similar catalytic properties to human protoporphyrinogen IX oxidase that also binds the common plant herbicide, acifluorfen. In the native structure, the planar porphyrinogen substrate is mimicked by a Tween 20 molecule, tracing three sides of the macrocycle. In contrast, acifluorfen does not mimic the planarity of the substrate but is accommodated by the shape of the binding pocket and held in place by electrostatic and aromatic interactions. A hydrophobic patch surrounded by positively charged residues suggests the position of the membrane anchor, differing from the one proposed for the tobacco mitochondrial protoporphyrinogen oxidase. Interestingly, there is a discrepancy between the dimerization state of the protein in solution and in the crystal. Conserved structural features are discussed in relation to a number of South African variegate porphyria-causing mutations in the human enzyme.     

Deviation of eyes and head in acute cerebral stroke

Background  

It is a well-known phenomenon that some patients with acute left or right hemisphere stroke show a deviation of the eyes (Prévost's sign) and head to one side. Here we investigated whether both right- and left-sided brain lesions may cause this deviation. Moreover, we studied the relationship between this phenomenon and spatial neglect. In contrast to previous studies, we determined not only the discrete presence or absence of eye deviation with the naked eye through clinical inspection, but actually measured the extent of horizontal eye-in-head and head-on-trunk deviation. In further contrast, measurements were performed early after stroke onset (1.5 days on average).     

Structural details on the binding of antihypertensive drugs captopril and enalaprilat to human testicular angiotensin I-converting enzyme

Angiotensin converting enzyme (ACE) plays a critical role in the circulating or endocrine renin-angiotensin system (RAS) as well as the local regulation that exists in tissues such as the myocardium and skeletal muscle. Here we report the high-resolution crystal structures of testis ACE (tACE) in complex with the first successfully designed ACE inhibitor captopril and enalaprilat, the Phe-Ala-Pro analogue. We have compared these structures with the recently reported structure of a tACE-lisinopril complex [Natesh et al. (2003) Nature 421, 551-554]. The analyses reveal that all three inhibitors make direct interactions with the catalytic Zn(2+) ion at the active site of the enzyme: the thiol group of captopril and the carboxylate group of enalaprilat and lisinopril. Subtle differences are also observed at other regions of the binding pocket. These are compared with N-domain models and discussed with reference to published biochemical data. The chloride coordination geometries of the three structures are discussed and compared with other ACE analogues. It is anticipated that the molecular details provided by these structures will be used to improve the binding and/or the design of new, more potent domain-specific inhibitors of ACE that could serve as new generation antihypertensive drugs.     

Angiotensin-converting enzyme-2 (ACE2): comparative modeling of the active site, specificity requirements, and chloride dependence

Angiotensin-converting enzyme 2 (ACE2), a homologue of ACE, represents a new and potentially important target in cardio-renal disease. A model of the active site of ACE2, based on the crystal structure of testicular ACE, has been developed and indicates that the catalytic mechanism of ACE2 resembles that of ACE. Structural differences exist between the active site of ACE (dipeptidyl carboxypeptidase) and ACE2 (carboxypeptidase) that are responsible for the differences in specificity. The main differences occur in the ligand-binding pockets, particularly at the S2' subsite and in the binding of the peptide carboxy-terminus. The model explains why the classical ACE inhibitor lisinopril is unable to bind to ACE2. On the basis of the ability of ACE2 to cleave a variety of biologically active peptides, a consensus sequence of Pro-X-Pro-hydrophobic/basic for the protease specificity of ACE2 has been defined that is supported by the ACE2 model. The dipeptide, Pro-Phe, completely inhibits ACE2 activity at 180 microM with angiotensin II as the substrate. As with ACE, the chloride dependence of ACE2 is substrate-specific such that the hydrolysis of angiotensin I and the synthetic peptide substrate, Mca-APK(Dnp), are activated in the presence of chloride ions, whereas the cleavage of angiotensin II is inhibited. The ACE2 model is also suggestive of a possible mechanism for chloride activation. The structural insights provided by these analyses for the differences in inhibition pattern and substrate specificity among ACE and its homologue ACE2 and for the chloride dependence of ACE/ACE2 activity are valuable in understanding the function and regulation of ACE2.