In situ hybridization of atrial natriuretic peptide mRNA in the endothelial cells of human umbilical vessels

The localization of mRNA encoding preproatrial natriuretic peptide (ANP) was investigated in cultured human umbilical vein endothelial cells (HUVEC) and tissue preparations of umbilical vein and artery. The techniques used were in situ hybridization and in situ hybridization combined with immunocytochemistry, using ³²P-radiolabelled and non-radioactive digoxigenin labelled complementary RNA probes. Human ANP mRNAs are mainly localized in the endothelial cells of the umbilical vein and, to a lesser extent, in the endothelial cells of the umbilical artery. The autoradiographic labelling and the intensity of digoxigenin staining were significantly reduced by treatment with RNase before in situ hybridization. This study provides unequivocal evidence for the expression of the ANP gene in the endothelial cells of human umbilical vessels, confirming that these endothelial cells have the ability to synthesize this peptide. The functional significance of the presence of the ANP mRNA in the endothelial cells of human umbilical vessels is discussed.     

TESTING INFERENCES ABOUT MICRO-EVOLUTIONARY PROCESSES BY MEANS OF SPATIAL AUTOCORRELATION ANALYSIS

We generated numerous simulated gene-frequency surfaces subjected to 200 generations of isolation by distance with, in some cases, added migration or selection. From these surfaces we assembled six data sets comprising from 12 to 15 independent allele-frequency surfaces, to simulate biologically plausible population samples. The purpose of the study was to investigate whether spatial autocorrelation analysis will correctly infer the microevolutionary processes involved in each data set. The correspondence between the simulated processes and the inferences made concerning them is close for five of the six data sets. Errors in inference occurred when the effect of migration was weak, due to low gene frequency differential or low migration strength; when selection was weak and against a background with a complex pattern; and when a random process—isolation by distance—was the only one acting. Spatial correlograms proved more sensitive to detecting trends than inspection of gene-frequency surfaces by the human eye. Joint interpretation of the correlograms and their clusters proved most reliable in leading to the correct inference. The inspection and clustering of surfaces were useful for determining directional components. Because this method relies on common patterns across loci, as many gene frequencies as feasible should be used. We recommend spatial autocorrelation analysis for the detection of microevolutionary processes in natural populations.     

History, Memory, and Nation in the (Post)Colonies

Represented Communities: Fiji and World Decolonization. John D. Kelly and Martha Kaplan. Chicago: University of Chicago Press, 2001. 243 pp.
Cultural Memory: Reconfiguring History and Identity in the Postcolonial Pacific. Jeannerte Marie Mageo. Honolulu: University of Hawai'i Press, 2001. 222 pp.
In Colonial New Guinea: Anthropological Perspectives. Naomi M. McPherson. ed. Pittsburgh: University of Pittsburgh Press, 2001. 264 pp.     

Cadmium replaces calcium in the cell wall ofUlva lactuca

Electron microscopy, in conjunction with X-ray microanalysis, was used to investigate the effects of exposure to cadmium on the elemental composition of the macroalgaUlva lactuca. The cell wall was the only region of the cell to show any marked change in chemical composition as a result of exposure to cadmium, with less calcium evident in cadmium-treated thallus compared with untreated thalli. The cell wall ofU. lactuca is a complex structure made up of polysaccharides consisting of many-branched chains composed mostly of rhamnose and galactose subunits. Some of the hydroxyl groups on the subunits are substituted by sulphate groups. Borate is associated with the rhamnose subunits, which contain no sulphate groups, and calcium binds to borate, cross-linking the rhamnose groups. The borate-calcium complex adds rigidity to the cell wall; the replacement of calcium by cadmium will, therefore, influence the rigidity of the thallus. The ecological significance of this work is discussed with respect to the ability of the alga to withstand grazing or emersion.     

Identification and partial characterization of α2-macroglobulin from the tuatara (Sphenodon punctatus)

α₂-Macroglobulin (α₂-M), a large molecular mass proteinase-binding protein, was identified in plasma from tuatara (Sphenodon), a rare reptile endemic to New Zealand. In this genus, α₂-M constitutes 11–13% of total plasma protein (∼2.2–3.9 mg/ml). Analysis of blood samples collected at approximately monthly intervals from individual tuatara indicated that the plasma level of α₂-M remains fairly constant. The subunits of tuatara α₂-M have an apparent molecular mass of ∼160 kDa as determined by SDS-polyacrylamide gel electrophoresis and the intact protein is an oligomer that contains inter-chain disulfide bonds. N-terminal sequence analyses of tuatara α₂-M revealed a distinct similarity to α-macroglobulins of other vertebrates and that at least two types of α₂-M subunits are present in plasma of tuatara.     

Cytochalasin Rearranges Cortical Actin of the Alga Nitella into Short, Stable Rods

The cortical cytoplasm of the alga Nitella contains reticulateactin that does not survive perfusion fixation with glutaraldehydeunless prestabilized with the cross-linker 3-maleimidobenzoyl-N-hydroxysuccinimidester (MBS). Cytochalasin D remodels thiscortical actin into short rods which are more stable, survivingaldehyde fixation without MBS pre-treatment. The overall alignmentof these actin rods correlates with that of cortical microtubules(transverse in young cells, random in old cells) but probablydoes not involve one-to-one correspondence. The time course,dose dependence and reversibility of these structural changesbroadly resemble those for streaming inhibition by cytochalasinbut the cortical actin responds to concentrations that do notslow streaming. Because the structural changes concern the corticaland not the subcortical actin, they seem unlikely to directlyinhibit streaming. Formation of cortical rods is not a responseto streaming inhibition per se since it does not occur whentwo other inhibitors of streaming (2,4-dinitrophenol (DNP) andNethyl maleimide (NEM)) are used. NEM, however, resembles MBSin stabilizing the reticulate form of cortical actin even thoughit cannot cross link. ¹Address from July 1995; Department of Biology, Faculty of Science,Osaka University, Machikaneyama 1-1, Tayonaka, Osaka, 560 Japan.     

Phylogeny and adaptive radiation within the Anomopoda: a preliminary exploration

The distinctness of the Anomopoda and the polyphyletic nature of the so-called Cladocera are emphasized.An attempt is made to reconstruct the ancestral anomopod, which probably lived in Palaeozoic times. This task is facilitated by the availability of detailed information on extant forms, which includes functional as well as purely morphological considerations and enables us to understand the means whereby complex mechanisms were transformed during evolution. Comparative studies on the ecology and habits of extant forms also throw light on the probable way of life of the ancestral anomopod.Adaptive radiation within the Anomopoda is briefly surveyed and an outline of the suggested phylogeny of the order is indicated.Institute of Environmental and Biological Sciences, University of Lancaster     

Effect of inhA and katG on isoniazid resistance and virulence of Mycobacterium bovis

Isoniazid (INH) resistance of the Mycobacterium tuberculosis Complex (MtbC) is associated with both loss of catalase activity and mutation of the inhA gene. However, the relative contributions of these changes to resistance and to the loss of virulence for guinea-pigs is unknown. In this study, a virulent strain of Mycobacterium bovis, a member of the MtbC., was exposed to increasing concentrations of INH. Two INH-resistant strains were produced which had lost catalase activity. Strain WAg405, which had a higher resistance to INH, also had a mutation in the inhA gene. This demonstrated that loss of catalase activity and mutation of inhA had a cumulative effect on INH resistance. When a functional katG gene was integrated into the genome of WAg405 the INH resistance was greatly reduced. This indicated that most of the resistance had been caused by loss of catalase activity. While the parent INH-sensitive strain was virulent for guinea-pigs, the INH-resistant strains were significantly less virulent. Integration of a functional katG gene into the most resistant strain restored full virulence. This clearly established that katG is a virulence factor for M. bovis and that mutation of the inhA gene has no effect on virulence.     

Molecular evolution of plant β-glucan endohydrolases

The evolutionary relationships of two classes of plant β-glucan endohydrolases have been examined by comparison of their substrate specificities, their three-dimensional conformations and the structural features of their corresponding genes. These comparative studies provide compelling evidence that the (1→3)-β-glucanases and (1→3,1→4)-β-glucanases from higher plants share a common ancestry and, in all likelihood, that the (1→3,1→4)-β-glucanases diverged from the (1→3)-β-glucanases during the appearance of the graminaceous monocotyledons. The evolution of (1→3,1→4)-β-glucanases from (1→3)-β-glucanases does not appear to have invoked ‘modular’ mechanisms of change, such as those caused by exon shuffling or recombination. Instead, the shift in specificity has been acquired through a limited number of point mutations that have resulted in amino acid substitutions along the substrate-binding cleft. This is consistent with current theories that the evolution of new enzymic activity is often achieved through duplication of the gene encoding an existing enzyme which is capable of performing the required chemistry, in this case the hydrolysis of a glycosidic linkage, followed by the mutational alteration and fine-tuning of substrate specificity. The evolution of a new specificity has enabled a dramatic shift in the functional capabilities of the enzymes. (1→3)-β-Glucanases that play a major role, inter alia, in the protection of the plant against pathogenic microorganisms through their ability to hydrolyse the (1→3)-β-glucans of fungal cell walls, appear to have been recruited to generate (1→3,1→4)-β-glucanases, which quite specifically hydrolyse plant cell wall (1→3,1→4)-β-glucans in the graminaecous monocotyledons during normal wall metabolism. Thus, one class of β-glucan endohydrolase can degrade β-glucans in fungal walls, while the other hydrolyses structurally distinct β-glucans of plant cell walls. Detailed information on the three-dimensional structures of the enzymes and the identification of catalytic amino acids now present opportunities to explore the precise molecular and atomic details of substrate-binding, catalytic mechanisms and the sequence of molecular events that resulted in the evolution of the substrate specificities of the two classes of enzyme.