Optimization of thiazole analogues of resveratrol for induction of NAD(P)H:quinone reductase 1 (QR1)

NAD(P)H:quinone reductase 1 (QR1) belongs to a class of enzymes called cytoprotective enzymes. It exhibits its cancer protective activity mainly by inhibiting the formation of intracellular semiquinone radicals, and by generating α-tocopherolhydroquinone, which acts as a free radical scavenger. It is therefore believed that QR1 inducers can act as cancer chemopreventive agents. Resveratrol (1) is a naturally occurring stilbene derivative that requires a concentration of 21 μM to double QR1 activity (CD = 21 μM). The stilbene double bond of resveratrol was replaced with a thiadiazole ring and the phenols were eliminated to provide a more potent and selective derivative 2 (CD = 2.1 μM). Optimizing the substitution pattern of the two phenyl rings and the central heterocyclic linker led to a highly potent and selective QR1 inducer 9o with a CD value of 0.087 μM.     

Optimizing thiadiazole analogues of resveratrol versus three chemopreventive targets

Chemoprevention is an approach to decrease cancer morbidity and mortality through inhibition of carcinogenesis and prevention of disease progression. Although the trans stilbene derivative resveratrol has chemopreventive properties, its action is compromised by weak non-specific effects on many biological targets. Replacement of the stilbene ethylenic bridge of resveratrol with a 1,2,4-thiadiazole heterocycle and modification of the substituents on the two aromatic rings afforded potential chemopreventive agents with enhanced potencies and selectivities when evaluated as inhibitors of aromatase and NF-κB and inducers of quinone reductase 1 (QR1).     

Boomeranging in structural defense: Phytophagous insect uses cycad trichomes to defend against entomophagy

Plant defensive behaviors that resist arthropod herbivory include trichome-mediated defenses, and variation in plant trichome morphology and abundance provides examples of the mechanistic complexities of insect-plant interactions. Trichomes were removed from Cycas revoluta cataphylls on the island of Guam to reveal Aulacaspis yasumatsui scale infestation, and predation of the newly exposed insects by pre-existing Rhyzobius lophanthae beetles commenced within one day. The quotient of predated/total scale insects was 0.5 by day 4 and stabilized at that found on adjacent glabrous leaves in about one week. The trichome phenotype covering the C. revoluta cataphyll complex offers the invasive A. yasumatsui armored scale effectual enemy-free space in this system. This pest and predator share no known evolutionary history with C. revoluta, therefore, the adaptive significance of this plant behavior in natural habitat is not yet known.     

Carica papaya (Caricaceae): a case study into the effects of domestication on plant vegetative growth and reproduction

Few studies have quantitatively evaluated the gender specific effects of cultivation on plant growth and reproduction. The availability of cultivated and wild populations of different genders of Carica papaya L. (Caricaceae) on Guam provided an opportunity to study these effects quantitatively. We compared the gender specific allometry of height vs. basal stem diameter (H vs. D), stem slenderness ratio (H/D), and the height at first flowering (H(fl)) of carpellate and staminate plants growing under natural conditions (N = 150 each) with those of carpellate and hermaphroditic plants (N = 250 each) from two cultivars (Sunrise and Tainung 2). These comparisons indicated that (1) wild carpellate and staminate plants are significantly taller than either gender of the two cultivars with equivalent D; (2) the scaling exponent governing the H vs. D relationship of both genders of wild plants is significantly higher than that of either cultivated gender; (3) cultivar type does not affect the H vs. D exponent, but gender expression does; (4) gender expression (but not cultivar-type) also affects H(fl) (cultivation substantially reduces carpellate plant H(fl)); and (5) the onset of sexual maturity is associated with a dramatic reversal in H/D ontogeny. Cultivation therefore has "condensed" patterns of vegetative growth in a gender specific manner, whereas gender expression alters both vegetative and reproductive growth significantly more so than does cultivar-type.     

Non-genomic transmission of paternal behaviour between fathers and sons in the monogamous and biparental California mouse

Maternal behaviour has profound, long-lasting implications for the health and well-being of developing offspring. In the monogamous California mouse (Peromyscus californicus), care by both parents is critical for offspring survival. We tested the hypothesis that similar to maternal care in rodents, paternal huddling and grooming (HG) behaviour can be transmitted to future generations via behavioural mechanisms. In California mice, testosterone maintains paternal HG behaviour. In the present study, we randomly assigned a group of male California mice to castration or sham-operated conditions and allowed them to raise their offspring normally. Adult sons of these males were paired with a female, and they were observed interacting with their own offspring. We found that like their fathers, the sons of castrated males huddled and groomed their young at lower levels than the sons of sham-operated fathers. The sons of castrates also retrieved pups more frequently. When both parents were present, the sons of castrates also showed a trend towards engaging in less exploratory behaviour. These data support the hypothesis that paternal behaviour, like maternal behaviour, can be transferred to future generations via epigenetic mechanisms and suggest that in a biparental species both parents contribute to offspring behavioural development.     

Axonal ephrinA/EphA interactions, and the emergence of order in topographic projections

In the classical view of axon guidance, neurons send out axons which are endowed with guidance receptors enabling them to find their (distant) target areas by an interaction with their ligands expressed in specific spatio-temporal patterns along their pathways and in their target area. However, this view has recently been confounded by more detailed analyses of, for example, the expression patterns of EphAs and ephrinAs in the retinotectal projection. Here ephrinA 'ligands' are expressed not only in the target area but also on the projecting RGC axons, and EphA 'receptors' not only on retinal ganglion cell (RGC) axons but also in the target area itself. This review describes the on-going functional characterisation of the surprising co-expression of ephrinAs and EphAs on retinal ganglion cell (RGC) axons and other cell types. It also investigates the function of ephrinAs as receptors and describes their interaction with co-receptors involved in mediating this function.     

Song acquisition in photosensitive and photorefractory male European starlings

We tested the ability of 1-year-old European starlings (Sturnus vulgaris) to acquire songs while in different physiological states. Photorefractory males, with low testosterone levels, learned songs as completely and as accurately as photosensitive males in full reproductive condition. This indicates that song acquisition in 1-year-old males does not depend on high levels of androgens. The ability to learn songs during the nonbreeding season may reflect the high song output of potential tutors through most of the year, including the photorefractory period, and may facilitate increases in song repertoire size in adulthood.     

Enantioselective reduction of 3,4-methylene-dioxyphenylacetone using Candida famata and Zygosaccharomyces rouxii

In an effort to prepare 3,4-methylene-dioxyphenyl-(S)-isopropanol from 3,4-methylene-dioxyphenylacetone, an initial screen of microbes indicated that Candida famata could catalyze this reaction efficiently at low substrate concentration. A dilute, large-scale process was developed to provide experimental material for the chemical synthesis to be explored. However, the productivity number of this process [0.134 g product (g␣wet␣weight cells)⁻¹ day⁻¹ was too low to be practical. C.␣famata was also extremely sensitive to concentrations of both the ketone and the alcohol greater than 2 g/l. A more extensive screen of yeast and fungi revealed that Zygosaccharomyces rouxii was more tolerant to higher substrate concentrations and had a higher productivity number [0.8 g (g wet weight cells)⁻¹ day⁻¹]. These characteristics suggested that Z. rouxii could be used in a large-scale process at high substrate concentrations. Received: 8 July 1996 / Received revision: 9 September 1996 / Accepted: 18 September 1996     

Trade Winds Reduce Growth and Influence Gas Exchange Patterns in Papaya Seedlings

Four experiments were conducted to determine the effect of tradewinds in Guam, USA, on growth and gas exchange of three papaya(Carica papaya L.) cultivars. ‘Known You 1’, ‘Sunrise’,and ‘Tainung 2’ papaya seedlings at two differentstages of development were exposed to 0, 36 or 100% ambientwind. Wind exposure reduced stem height and leaf or stem dryweight in most cases, but had little influence on root growth.Net CO₂assimilation (A_CO2) at midday was lower for seedlingsexposed to wind than for those protected from wind. Dark respirationof exposed seedlings increased as much as 120% above that ofthe protected seedlings during the night. Wind exposure decreasedwhole plant evapotranspiration by up to 36% during the photoperiod,but increased evapotranspiration by 58–87% during thenocturnal period. Responses to wind exposure were similar amongcultivars, except that growth of ‘Tainung 2’ seedlingswas less affected by wind than that of the other cultivars.Seedlings that were exposed to the various wind treatments fromgermination onwards were less influenced by wind exposure thanwere seedlings that were grown in a protected nursery beforebeing exposed to the various wind treatments. These data indicatethat: (1) ambient trade winds in Guam are strong enough to decreasethe growth of papaya seedlings; (2) plant age influences theresponse; (3) stem and leaf growth are more influenced thanroot growth; and (4) decreasedA_CO2 and increased dark respirationmay be partly responsible for growth reduction. Copyright 2001Annals of Botany Company Carica papaya, gas exchange, wind     

A comparison between the record height-to-stem diameter allometries of Pachycaulis and Leptocaulis species

BACKGROUND AND AIMS: The interspecific allometry of maximum plant height (Hmax) with respect to maximum basal stem diameter (Dmax) has been studied for leptocaulis dicot and conifer tree species. In contrast, virtually nothing is known about the interspecific allometry of pachycaulis species. Here, the interspecific allometries for palms, cacti and cycads are reported and compared with those of leptocaulis dicot and conifer tree species to determine whether pachycauly limits Hmax with respect to Dmax. METHODS: Data for each of a total of 1461 pachycaulis and leptocaulis species were gathered from the primary literature. The scaling exponent and the allometric constant of logHmax vs. logDmax reduced major axis regression curves (and their respective 95 % confidence intervals) were used to compare the four species groups. The stem slenderness ratio (Hmax/Dmax = Rmax) for each species was also computed to compare interspecific trends in trunk shape. KEY RESULTS AND CONCLUSIONS: Each of the four species groups is allometrically unique, i.e. no single 'canonical' maximum plant height to stem diameter allometry exists across all four species groups. Although pachycaulis does not intrinsically limit height, height is nevertheless limited by the size range of basal stem diameter occupied by each species group. Pachycaulis species achieve heights comparable to some leptocaulis species by virtue of very high slenderness ratios attended by an absence or paucity of stem branching. The diversity observed for pachycaulis stem allometries is likely the result of the independent evolutionary origins of this growth habit and the different anatomical strategies used to stiffen stems.