Book reviews

Patterns of thought in Africa and the West: Essays on magic, religion and science , by Robin Horton. Cambridge University Press, Cambridge, 1997. xi, 471pp., figures, notes, bibliography, index. ISBN 0–521–36926–6 (paperback).

Women's experiences with HIV/AIDS: An international perspective , edited by Lynellyn D. Long and E. Maxine Ankrah. Columbia University Press, New York, 1996. x, 426pp., tables, references, notes on contributors, index. ISBN 0–231–10605‐X (paperback).

A healing place: Indigenous visions for personal empowerment and community recovery , by Kayleen M. Hazelhurst. Central Queensland University Press, Rockhampton, 1996. xiii, 274pp., notes, illustrations, references. ISBN 0–908140–87–8 (paperback).

Reading the skin: Adornment, display and society among the Wahgi , by Michael O'Hanlon. Crawford House Press, Bathurst, 1989. 139pp., map, photographs, orthography and kinship terms, glossary, notes, bibliography, index. ISBN 1–86333–003–8 (hardback).

Paradise: Portraying the New Guinea Highlands , by Michael O'Hanlon. Crawford House Press, Bathurst, 1993. 99pp., maps, photographs, notes, bibliography, index. ISBN 1–86333–078‐X (paperback).

To sing with pigs is human: The concept of person in Papua New Guinea , by Jane C. Goodale. University of Washington Press, Seattle, 1995. xvi, 269pp., map, tables, figure, musical scores, photographs, bibliography, index. ISBN 0–295–94736–2 (paperback).

Resplendent sites, discordant voices: Sri Lankans and international tourism , by Malcolm Crick. Harwood Academic Publishers, Chur, 1994. x, 237pp., maps, tables, photographs, bibliography, index. ISBN 3–7186–5564–0 (hardback).

Impasse of the angels: Scenes from a Moroccan space of memory , by Stefania Pandolfo. University of Chicago Press, Chicago, 1997. xi, 389pp., photograph, notes, index. ISBN 0–226–64532–0 (paperback).

Mal'uocchiu: Ambiguity, evil eye, and the language of distress , by Sam Migliore. University of Toronto Press, Toronto, 1997. xiv, 159pp., tables, figures, glossary, notes, bibliography, index. ISBN 0–8020–7922–9 (paperback).

Satmar: Two generations of an urban island: The life, thought and culture of an Hasidic Jewish community in America , by Israel Rubin. Peter Lang, New York, 1997. xii, 341pp., tables, figures, notes, index. ISBN 0–8204–0759–3 (hardback).

UFO crash at Roswell: The genesis of a modern myth , by Benson Saler, Charles A. Ziegler and Charles B. Moore. Smithsonian Institution Press, Washington DC, 1997. xii, 198pp., maps, tables, figures, appendices, notes, bibliography, index. ISBN 1–56098–751–0 (hardback).     

Multiple aminoacyl-tRNA synthetases (translases) in temperature acclimation of eurythermal fish

The temperature dependency of activity of the entire set of aminoacyl-tRNA synthetases (protein synthetic translases) has been studied in the laboratory rat and in toadfish (Opsanus tau) acclimated to 20 δC or to 10 δC. The complex temperature responses of these enzyme systems reveal the presence of multiple forms for the translases of most amino acids and show adaptive behavior of these systems with respect to body temperature of the animal. The phenylalanine translase system has been studied in detail, and adaptation of this system at low temperatures correlates with adaptation in the elongation factor system. All known protein synthetic components appear to be coordinated in adaptive responses with the exception of ribosomes. Our data indicate no rôle for ribosomes in adaptation of the protein synthetic system and apparently no rôle for ribosomes in protein synthesis at all in rat and fish. This finding may solve some long-standing paradoxes in the protein synthesis field concerning the mechanism by which ribosomes participate in protein synthesis.     

Cell cycle regulator Cdc14 is expressed during sporulation but not hyphal growth in the fungus-like oomycete Phytophthora infestans

Cdc14 proteins are important regulators of mitosis and the cell cycle. These phosphatases have been studied previously only in yeasts and metazoans, which grow by fission or budding. Here we describe a homologue (piCdc14) from the oomycete Phytophthora infestans, a primitive eukaryote lacking a classical cell cycle. PiCdc14 complements a cdc14ts mutant of Saccharomyces cerevisiae and may function like other Cdc14 proteins, but displays a strikingly different pattern of expression. Whereas previously studied Cdc14 genes are constitutively transcribed, piCdc14 is not expressed during normal growth but instead only during asexual sporulation. In transformants of P. infestans expressing a fusion between the piCdc14 promoter and the -glucuronidase reporter, expression was first detected in sporangiophore initials, persisted in sporangiophores bearing immature sporangia, and later became restricted to mature sporangia. After germination, expression ended a few hours before the resumption of mitosis in hyphae emerged from the spores. Homology-dependent silencing experiments supported an essential role of piCdc14 in sporulation. It is proposed that the function of piCdc14 may be to synchronise nuclear behaviour during sporulation and maintain dormancy in spores until germination. These results help illuminate the process of sporulation in oomycetes and the evolution of the cell cycle in eukaryotes.     

Quantification of allosteric influence of Escherichia coli phosphofructokinase by frequency domain fluorescence

The allosteric properties of the wild-type Escherichia coli phosphofructokinase were compared to the E187A mutant by using frequency-domain techniques. Tryptophan-shifted mutants comprising of double (W311Y/Y55W and W/311F/F188W) and triple (W311Y/Y55W/E187A and W311F/F188W/E187A) amino acid residue changes, which allowed for better fluorescence probing at targeted sites, were also compared to the wild-type and E187A. The additive nature of multiple mutations allowed one to partition the net effect of modifying residue 187. In general, the mutant enzymes displayed greater heterogeneity in sub-state population than did the wild-type enzyme. The semi-cone angle model was used to quantify the extent of depolarization of the fluorophore. Use of the model presupposes that the extent of depolarization directly correlates with the degree of flexibility of the fluorophore. A relationship has been established between the values determined from the semi-cone angle calculations and the thermodynamic components responsible for the allosteric linkage between the regulatory and substrate binding. Coupling interactions giving rise to positive entropy components are manifested by increasing flexibility of the ternary complexes rather than the binary complexes.     

Subcellular targeting of nine calcium-dependent protein kinase isoforms from Arabidopsis

Calcium-dependent protein kinases (CDPKs) are specific to plants and some protists. Their activation by calcium makes them important switches for the transduction of intracellular calcium signals. Here, we identify the subcellular targeting potentials for nine CDPK isoforms from Arabidopsis, as determined by expression of green fluorescent protein (GFP) fusions in transgenic plants. Subcellular locations were determined by fluorescence microscopy in cells near the root tip. Isoforms AtCPK3-GFP and AtCPK4-GFP showed a nuclear and cytosolic distribution similar to that of free GFP. Membrane fractionation experiments confirmed that these isoforms were primarily soluble. A membrane association was observed for AtCPKs 1, 7, 8, 9, 16, 21, and 28, based on imaging and membrane fractionation experiments. This correlates with the presence of potential N-terminal acylation sites, consistent with acylation as an important factor in membrane association. All but one of the membrane-associated isoforms targeted exclusively to the plasma membrane. The exception was AtCPK1-GFP, which targeted to peroxisomes, as determined by covisualization with a peroxisome marker. Peroxisome targeting of AtCPK1-GFP was disrupted by a deletion of two potential N-terminal acylation sites. The observation of a peroxisome-located CDPK suggests a mechanism for calcium regulation of peroxisomal functions involved in oxidative stress and lipid metabolism.     

Cooperative effects of Th2 cytokines and allergen on normal and asthmatic bronchial epithelial cells

In sensitized individuals, exposure to allergens such as Dermatophagoides pteronyssinus (Der p) causes Th2 polarization and release of cytokines, including IL-4 and IL-13. Because Der p extracts also have direct effects on epithelial cells, we hypothesized that allergen augments the effects of Th2 cytokines by promoting mediator release from the bronchial epithelium in allergic asthma. To test our hypothesis, primary bronchial epithelial cultures were grown from bronchial brushings of normal and atopic asthmatic subjects. RT-PCR showed that each culture expressed IL-4R(alpha), common gamma-chain, and IL-13R(alpha)(1), as well as IL-13R(alpha)(2), which negatively regulates IL-13 signaling; FACS analysis confirmed IL-13R(alpha)(2) protein expression. Exposure of epithelial cultures to either Der p extracts, TNF-alpha, IL-4, or IL-13 enhanced GM-CSF and IL-8 release, and this was partially suppressible by corticosteroids. Simultaneous exposure of the epithelial cultures to IL-4 or IL-13 together with Der p resulted in a further increase in cytokine release, which was at least additive. Release of TGF-alpha was also increased by TNF-alpha and combinations of IL-4, IL-13, and Der p; however, this stimulation was only significant in the asthma-derived cultures. These data suggest that, in an allergic environment, Th2 cytokines and allergen have the potential to sustain airway inflammation through a cooperative effect on cytokine release by the bronchial epithelium. Our novel finding that IL-4, IL-13, and allergen enhance release of TGF-alpha, a ligand for the epidermal growth factor receptor that stimulates fibroblast proliferation and goblet cell differentiation, provides a potential link between allergen exposure, Th2 cytokines, and airway remodelling in asthma.     

A positive feedback loop stabilizes the guanine-nucleotide exchange factor Cdc24 at sites of polarization

In Saccharomyces cerevisiae, activation of Cdc42 by its guanine-nucleotide exchange factor Cdc24 triggers polarization of the actin cytoskeleton at bud emergence and in response to mating pheromones. The adaptor protein Bem1 localizes to sites of polarized growth where it interacts with Cdc42, Cdc24 and the PAK-like kinase Cla4. We have isolated Bem1 mutants (Bem1-m), which are specifically defective for binding to Cdc24. The mutations map within the conserved PB1 domain, which is necessary and sufficient to interact with the octicos peptide repeat (OPR) motif of Cdc24. Although Bem1-m mutant proteins localize normally, bem1-m cells are unable to maintain Cdc24 at sites of polarized growth. As a consequence, they are defective for apical bud growth and the formation of mating projections. Localization of Bem1 to the incipient bud site requires activated Cdc42, and conversely, expression of Cdc42-GTP is sufficient to accumulate Bem1 at the plasma membrane. Thus, our results suggest that Bem1 functions in a positive feedback loop: local activation of Cdc24 produces Cdc42-GTP, which recruits Bem1. In turn, Bem1 stabilizes Cdc24 at the site of polarization, leading to apical growth.     

Receptors in the Ventral Tegmental Area Mediating Nicotine-Induced Dopamine Release in the Nucleus Accumbens

Nicotine or cocaine, when administered intravenously, induces an increase of extracellular dopamine in the nucleus accumbens. The nicotine-mediated increase was shown to occur at least in part through increase of the activity of dopamine neurons in the ventral tegmental area. As part of our continuing studies of the mechanisms of nicotine effects in the brain, in particular, effects on reward and cognitive mechanisms, in the present study we examined the role of various receptors in the ventral tegmental area in nicotine and cocaine reward. We assayed inhibition of the increase of dopamine in the nucleus accumbens induced by intravenous nicotine or cocaine administration by antagonists administered into the ventral tegmental area. Nicotine-induced increase of accumbal dopamine release was inhibited by intrategmental nicotinic (mecamylamine), muscarinic (atropine), dopaminergic (D₁: SCH 23390, D₂: eticlopride), and NMDA glutamatergic (MK 801) and GABA_B (saclofen) antagonists, but not by AMPA-kainate (CNQX, GYKI-52466) antagonists under our experimental circumstances. The intravenous cocaine-induced increase of dopamine in the nucleus accumbens was inhibited by muscarinic (atropine), dopamine 2 (eticlopride), and GABA_B (saclofen) antagonists but not by antagonists to nicotinic (mecamylamine), dopamine D₁ (SCH 23390), glutamate (MK 801), or AMPA-kainate (CNQX, GYKI-52466) receptors. Antagonists administered in the ventral tegmental area in the present study had somewhat different effects when they were previously administered intravenously. When administered intravenously atropine did not inhibit cocaine effects. The inhibition by atropine may be indirect, since this compound, when administered intrategmentally, decreased basal dopamine levels in the accumbens. The findings indicate that a number of receptors in the ventral tegmental area mediate nicotine-induced dopamine changes in the nucleus accumbens, a major component of the nicotine reward mechanism. Some, but not all, of these receptors in the ventral tegmental area also seem to participate in the reward mechanism of cocaine. The importance of local receptors in the ventral tegmental area was further indicated by the increase in accumbal dopamine levels after intrategmental administration of nicotine or also cocaine.