bluuebunny/crossref_metadata_2025 huggingface dataset:
Short‐term and long‐term effects of food supply on parasite burdens in Tawny Owls, Strix aluco
Authors: Appleby B. M. , Anwar M. A. , Petty S. J.
Published: March 2003

1. The relationships among food supply (Field Voles, Microtus agrestis), reproduction and blood parasites was investigated in Tawny Owls, Strix aluco, in Kielder Forest, Northumberland, in 1994 and 1995. Vole populations were significantly lower in 1995 than in 1994.

2. Birds did not lose parasites after initial infection, and the level at which infections were maintained was characteristic of individual birds.

3. In 1994, the number and intensity of parasites was higher in adult owls that had experienced low food supply when they themselves were reared. This indicated that food supplied to chicks in the nest has a long‐term effect on the parasite burden of adults.

4. In addition, there was evidence that parasite burdens of adults were influenced by their current food supply. Birds that suffered a decline in food abundance on their territories between 1994 and 1995 showed an increase in parasite load over the same period. In 1995, there was also a significant negative correlation between the parasite loads of owls and vole abundance on their territories.

5. The best predictor of parasite number of chicks reared in 1995 was the parasite load of their fathers. The parasites chicks developed were not the parasites with which their fathers were heavily infested. This result could be due to inherited immunity.

6. Our results indicated that food resources should be measured when investigating interactions between parasites and their hosts, and that offspring quality as well as quantity might suffer when food abundance is low.
Effects of foraging mode and season on the energetics of the Marine Iguana, Amblyrhynchus cristatus
Authors: Drent J. , Van Marken Lichtenbelt W. D. , Wikelski M.
Published: March 2003

1. Marine Iguanas (Amblyrhynchus cristatus) inhabiting the rocky shores of the Galápagos Islands apply two foraging strategies, intertidal and subtidal foraging, in a seasonal climate. Effects of both foraging strategy and seasonality on the daily energy expenditure (DEE) were measured using doubly labelled water.

2. Difference in foraging mode did not result in significant differences in DEE.

3. On Santa Fé the DEE in the warm season was significantly higher than in the cool season (67·8 ± 21·8 kJ kg–0·8 day–1vs 38·0 kJ kg–0·8 day–1). This difference can be explained by body temperature. A model estimate of the body temperature was used to predict monthly DEE figures, giving a year round budget. On average a 1‐kg iguana would need only 47 kJ day–1, or 17 mJ year –1. This is lower than previous estimates in which body temperatures were not taken into account.

4. The water flux of the Marine Iguana increases with increasing foraging time. The linear rise per minute foraging is roughly two times as high for subtidally foraging animals as for intertidal foragers.
Insectivore life histories: further evidence against an optimum body size for mammals
Authors: Symonds M. R. E.
Published: March 2003

1.This study tests a model of the relationship of body mass to reproductive power (the rate of conversion of energy from the environment to an organism’s offspring). Specifically tested is the prediction that the regression of life‐history variables on body size will change slope and sign about an ‘optimum’ body mass of 100 g.

2.Life‐history data from the mammalian order Insectivora have been collated and analysed using a phylogenetic comparative method to test this prediction.

3.The analyses showed little evidence for significant changes in slope or sign around 100g body mass, or other possible optimal body masses, contradicting the predictions of the model. These findings agree with those of similar analyses on life‐history variables of bats.
Daily energy expenditure of free‐living male Wood Mice in different habitats and seasons
Authors: Corp N. , Gorman M. L. , Speakman J. R.
Published: March 2003

1. The daily energy expenditure of free‐living adult male Wood Mice, Apodemus sylvaticus, from deciduous woodland and maritime sand‐dune was estimated using the doubly labelled water (DLW) technique and time–energy budget models.

2. Method of calculation had a small effect on the calculated energy demands. There were no significant differences in energy expenditure across sites or seasons despite large differences in home range among mice from different sites. Mice in winter, and on the sand‐dunes, had lower body masses, which offset the effects of larger home ranges and colder temperatures.

3. The daily energy expenditure for a Wood Mouse of mean body mass (20·5 g) was 67·9 kJ day–1 (n = 19) This was comparable to other similar size rodents (slightly higher), and did not deviate significantly from allometric predictions.

4. Variation in daily energy expenditure among individuals was not explained by ambient temperature, home range size, body mass, change in body mass, time spent active and the distance or speed of travel.

5. Sustainable metabolic rates approximated to five times basal metabolism and were within the range previously reported but higher than most other estimates of free‐living energy demands.

6. Rates of water influx and efflux were significantly greater for Wood Mice on the sand‐dunes (influx, 9·3 ± 1·14 ml day–1, efflux, 10·2 ± 1·10 ml day–1) than for animals in the woodland (influx, 6·3 ± 0·48 ml day–1, efflux, 6·2 ± 0·47 ml day–1). This was probably due to differences in the water content of their diets (seed in woodland and invertebrate on the sand‐dunes).

7. The time–energy budget models yielded estimates of energy expenditure considerably lower than the doubly labelled water estimate. Potential reasons for this discrepancy are discussed.
Do plant species with high relative growth rates have poorer chemical defences?
Authors: Almeida‐Cortez J. S. , Shipley B. , Arnason J. T.
Published: March 2003

1. Most theories of plant strategies assume the presence of certain ‘trade‐offs’. One such evolutionary trade‐off assumes a decrease in growth rate with increasing investment in chemical defences in species adapted to different levels of habitat fertility.

2. To test this hypothesis, we grew 31 herbaceous species of Asteraceae under controlled conditions of temperature (25 °C), humidity (80%), light (500 μmol m–2 s–1) and photoperiod (16 h day–1) in a modified Hoagland hydroponic solution. The plants grew from seed for 35 days post‐germination and were harvested at 14, 21, 28 and 35 days. Relative growth rate (RGR) was calculated as well as a general measure of potential phytochemical toxicity (LC50) using an alcohol extraction of secondary compounds followed by Brine Shrimp bioassay and an assay of total phenolics.

3. The interspecific correlation between RGR and the potential phytochemical toxicity was weak and non‐significant (rS = 0·12, P = 0·53). The correlation between RGR and total phenolics was weak, positive but significant (rS = 0·40, P = 0·03).

4. These results suggest that such an evolutionary trade‐off does not exist in this group of Asteraceae.
Field studies of reptile thermoregulation: how well do physical models predict operative temperatures?
Authors: R. Shine , M. Kearney
Published: March 2003

1. Field‐based studies on reptile thermoregulation increasingly rely upon physical models to estimate operative temperatures. Some investigators use models that mimic the size, shape, colour and posture of their study species, but such details may have little influence on thermal regimes (and hence, complex models may be a waste of time and money).

2. Temperatures were measured at 10‐min intervals inside 48 hollow copper‐pipe models exposed to natural weather conditions over a 27‐day period, in a factorial design to examine the effects of model attributes on thermal profiles.

3. These data clarify the ways in which model size, colour (reflectance), orientation and degree of contact with the substrate affect (a) mean, minimum and maximum temperatures, and (b) the number of hours per day that the models exceed specified thermal thresholds. Also examined are (c) interactions between model attributes in these respects, and (d) the ways in which such effects depend upon local weather conditions.

4. Model temperatures were affected by all of the attributes tested, but with few interactions between these effects. Although statistically significant, the effects of model attributes upon operative temperature regimes were generally minor (<5% of mean values).

5. Guidelines for the use of physical models in future research are provided.
Germination of CO2‐enriched Pinus taeda L. seeds and subsequent seedling growth responses to CO2 enrichment
Authors: Hussain M. , Kubiske M. E. , Connor K. F.
Published: March 2003

Pinus taeda seeds, developed under ambient or elevated (ambient + 200 µl l−1) [CO2], were collected from Duke Forest, North Carolina, USA in October 1998. Seeds were germinated in nutrient‐deficient soil in either ambient or elevated [CO2] (ambient + 200 µl l−1) greenhouse chambers and allowed to grow for 120 days.

 Seeds that developed in elevated [CO2] had 91 and 265% greater weight and lipid content, respectively, and three times the germination success, compared to those developed in current ambient [CO2].

 Seedlings from the elevated [CO2] seed source had significantly greater root length and more needles regardless of greenhouse chamber, but there were no treatment effects on tissue or total biomass.

 Severely limiting nutrient conditions resulted in significant photosynthetic downregulation by seedlings grown in greenhouse chambers with elevated [CO2], regardless of seed source.

 Our hypothesis that greater seed reserves from CO2 enrichment would synergistically affect seedling growth responses to elevated [CO2] was not strongly supported. Nonetheless, seeds produced in a CO2‐enriched environment may have fundamental changes in their viability, chemistry and germination that may affect reproduction.
Genetic variation in thermal tolerance among natural populations of Drosophila buzzatii: down regulation of Hsp70 expression and variation in heat stress resistance traits
Authors: Sørensen J. G. , Dahlgaard J. , Loeschcke V.
Published: March 2003

Thermal adaptation was investigated in the fruitfly Drosophila buzzatii Patterson and Wheeler. Two natural populations originating from a high‐ and a low‐temperature environment, respectively, were compared with respect to Hsp70 (heat shock protein) expression, knock‐down resistance and heat shock resistance.

 Three main hypotheses were tested: (i) The expression level of Hsp70 in flies from the high‐temperature habitat should be down‐regulated relative to flies from the colder habitat. (ii) Flies having higher Hsp70 expression levels should be weakened most by a hardening treatment and go faster into coma, as Hsp70 level reflects stress intensity, and therefore display reduced heat knock‐down resistance. (iii) Heat shock resistance should be increased in the population with highest Hsp70 expression because the level of Hsp70 is positively associated with this trait.

 The results generally matched the hypotheses. Hsp70 expression was reduced in the high‐temperature population. Knock‐down resistance was higher in the high‐temperature population and survival after heat shock was lower in the high‐temperature population.

 This study showed genetic differences in thermal tolerance between populations, indicating that high temperature in nature may be an important selective factor. Moreover, knock‐down resistance in this study seems to be a more relevant trait than standard heat shock resistance for identifying thermal adaptation in natural populations.
The specialist seed predator Bruchidius dorsalis (Coleoptera: Bruchidae) plays a crucial role in the seed germination of its host plant, Gleditsia japonica (Leguminosae)
Authors: Takakura K.
Published: March 2003

This paper describes the germination mechanism of hard seeds of a species of honey locust, Gleditsia japonica, which can germinate only when externally damaged, in relation to four germinating factors: feeding damage by two specialist seed predators, a bean weevil (Bruchidius dorsalis) and a cydid bug (Adrisa magna); feeding damage by a generalist seed predator, a wild mouse (Apodemus speciosus); and physical damage.

 In laboratory experiments, both the bean weevil and physical damage facilitated germination, while damage by the cydid bug and wild mouse did not.

 In contrast to laboratory findings, field censuses of G. japonica seed survival revealed that more than 99% were damaged either by B. dorsalis or A. magna. Therefore, less than 0·5% of the seeds remained intact, preventing formation of a seed bank.

 In addition, all germinating seeds found in the field contained B. dorsalis larvae.

 These results strongly suggest that damage by B. dorsalis is a prerequisite for G. japonica germination, in contrast to the conventional view that physical disturbance, possibly flooding, is the primary germinating factor for hard seeds.
Adjustment of tree structure in response to the environment under hydraulic constraints
Authors: Magnani F. , Grace J. , Borghetti M.
Published: March 2003

1. The hypothesis is tested that functional limitations, possibly related to the risk of disruptive xylem embolism, maintain the leaf water potential of trees within a safety range. This strategy would particularly apply to conifers.

2. It is also hypothesized that homeostasis in water transport is achieved by a combination of short‐term stomatal regulation and the optimal allocation of resources between transpiring foliage, conductive sapwood and absorbing roots.

3. The implications of this hypothesis for responses of plant structure to the environment are explored from a theoretical viewpoint, focusing in particular on the effects of temperature, vapour pressure deficit and soil water availability and texture.

4. A comparison with published data sets confirms model predictions of greater allocation to transpiring foliage with increasing temperature, and lower allocation with increasing vapour pressure deficit and soil drought. Allocation to fine roots would respond more strongly to drought, and the effect would be magnified by coarse soil textures.

5. The applicability of the model to other taxa remains to be determined, and the extent to which the observed structural adjustment is the result of phenotypic plasticity or long‐term adaptation is still unclear.
Insects as leaf engineers: can leaf‐miners alter leaf structure for birch aphids?
Authors: Johnson S. N. , Mayhew P. J. , Douglas A. E. , Hartley S. E.
Published: March 2003

This study examined the indirect impacts of leaf‐mining insects, Eriocrania spp. Zeller (Lepidoptera: Eriocraniidae) on a phloem‐feeding insect, Euceraphis betulae Koch (Homoptera: Drepanosiphinae). While many insect herbivores affect one another through changes to host plant chemical composition, Eriocrania also has the potential to affect E. betulae through structural modification of a shared leaf.

Euceraphis betulae mortality was higher when caged on leaves with Eriocrania leaf‐miners. Mortality was not affected by the amount of leaf mined or elevated phenolic compound concentrations in mined leaves, but leaf‐miner induced damage to the midrib was strongly correlated with poor aphid survival. In field surveys, E. betulae was significantly less abundant on mined leaves with midrib damage than on mined leaves with just lamina damage, or mine‐free leaves.

Experiments simulating leaf‐miner damage on B. pendula leaves pinpointed midrib damage as being associated with higher E. betulae mortality, whereas lamina damage had no effect on aphid mortality. Disruption of phloem hydraulics is proposed as the mechanism underpinning the negative impacts on the aphid.

Eriocrania larvae mining leaves with manually damaged midribs weighed more than those in which the midrib was intact. There was also a trend towards higher nitrogen concentrations in leaves in which Eriocrania had damaged the midrib. There could therefore be a selective advantage to leaf‐miners that damage the midrib if severance improves leaf nutritional quality, in addition to rendering the leaves unsuitable to potential competitors.
Determinants of postfire flowering in the geophytic grass Ehrharta capensis
Authors: Verboom G. A. , Stock W. D. , Linder H. P.
Published: March 2003

We conducted a fertilization–defoliation experiment to investigate postfire flowering in Ehrharta capensis, a cormous grass native to the Cape fynbos.

Combined fertilization and defoliation produced a strong flowering response in E. capensis, suggesting that the strong postfire flowering pattern of this species can be explained largely by the effect of fire on soil nutrients and vegetation cover. Flowering was absent in control plants, and sparse in plants receiving single treatments.

Comparable treatment dependence of flowering was not observed in two congeneric species that lack specialized storage structures and in which flowering is not apparently fire‐dependent.

In E. capensis, flowering did not significantly reduce the dry mass of corms persisting from previous years, or the amounts of reserves these contained. We conclude that corm‐stored reserves do not contribute substantially to inflorescence production.

Flowering E. capensis plants produced significantly larger replacement corms than did nonflowering plants, indicating that sexual reproduction does not occur at a cost to asexual persistence.

The lack of a trade‐off between sexual and asexual reproduction may explain why E. capensis, and possibly other clonal geophytes, flower only when resource availability is high. Cost–benefit models, which predict a trade‐off, do not properly describe resource allocation in these species.
Phenotypic plasticity of body size at different temperatures in a planktonic rotifer: mechanisms and adaptive significance
Authors: Stelzer C. P.
Published: March 2003

Larger body size at low temperatures is a commonly observed phenomenon in ectothermic organisms. The mechanisms that lead to this pattern and its possible adaptive significance were studied in laboratory experiments using the parthenogenetically reproducing rotifer Synchaeta pectinata.

At low temperatures of 4 °C mean body volume was 46% larger than in individuals cultured at 12 °C. Egg volume was 35% larger in low vs high temperatures.

Larger body size at low temperatures was caused by two mechanisms. First, when exposed to low temperatures, mothers laid larger eggs and the hatchlings of these eggs developed into larger adults (irrespective of temperature). Second, individuals cultured at low temperatures grew to a larger body size during their juvenile phase. The former mechanism had a greater influence on adult size than the latter.

The production of larger eggs at low temperatures seemed to be due to a higher reproductive investment into individual offspring as it occurred independently of differences in maternal size.

Life table experiments showed that offspring from small eggs (produced at high temperatures) had a significantly higher population growth rate than offspring from large eggs, when cultured at high temperatures. This was mainly due to an increase in fertility during the first days of adult life.
Quantifying woodland structure and habitat quality for birds using airborne laser scanning
Authors: Hinsley S. A. , Hill R. A. , Gaveau D. L. A. , Bellamy P. E.
Published: March 2003

Vegetation height across a 157‐ha deciduous woodland was estimated using an airborne remote‐sensing technique, airborne laser scanning (ALS), and the data obtained were used to produce a three‐dimensional map of the canopy surface of the entire wood.

Field‐based estimates of a tree canopy density index were compared with mean vegetation height calculated from the ALS data for sample areas of 54 × 54 m2 centred on each of 36 nestboxes within the wood. Canopy density index increased with mean vegetation height, such that height explained 86% of the variation in the density index. Thus remote‐sensed height could be used as a surrogate for the field‐based estimates.

Mean chick masses (mass being used as a measure of habitat quality) for Great Tits (Parus major L.) and Blue Tits (P. caeruleus L.) using the boxes were also examined in relation to the ALS mean vegetation height for the same sample areas.

For Blue Tits, mean chick mass at 11 days of age increased with vegetation height around the nestbox, but for Great Tits, the relationship was negative. Possible reasons for this difference are discussed, but the results should be treated with caution because sample sizes were small.

The application of ALS in woodland ecology is discussed.
Are associational refuges species‐specific?
Authors: Hambäck P. A. , Pettersson J. , Ericson L.
Published: March 2003

Associational refuges – reduced herbivory on plants in presence of other plant species – may be caused by general and species‐specific plant characteristics. However, the species specificity of associational refuges has rarely been evaluated.

This study examined the species specificity of one known example of associational refuges, the forb Lythrum salicaria and the monophagous insect herbivores Galerucella calmariensis, G. pusilla and Nanophyes marmoratus. The underlying mechanism was examined in order to evaluate connections between mechanisms and species specificity.

Laboratory studies showed that N. marmoratus but not Galerucella individuals were attracted by odour from undamaged host plants, and that neither species was distracted by odour from Myrica gale.

Field experiments showed that three non‐host plant neighbours with an appearance similar to M. gale, and artificial shrubs, reduced the abundance and egg‐laying of Galerucella species by 70–90%. The abundance of N. marmoratus was increased 18‐fold on plants in thickets compared with outside.

. The different responses by N. marmoratus and the Galerucella species to plant neighbours appear to be because N. marmoratus, but not Galerucella, uses olfactory information in the initial host‐finding process.
Foraging effort in relation to the constraints of reproduction in free‐ranging albatrosses
Authors: Shaffer S. A. , Costa D. P. , Weimerskirch H.
Published: March 2003

Theoretical models predict that animals will vary their effort to maximize different currencies such as time and energy when the constraints of reproduction change during breeding, but this has been poorly studied in free‐ranging animals.

Foraging effort (energy per unit time) was examined by comparing mass changes, foraging costs and activity‐specific behaviours of Wandering Albatrosses (Diomedea exulans Linnaeus) during the incubation and chick‐brooding stages. In 1998, 38 albatrosses (20 during incubation and 18 during brooding) were injected with doubly labelled water and equipped with satellite transmitters and activity data loggers.

During incubation, albatrosses travelled 3·7 times farther and were at sea 3·2 times longer, yet foraging costs were significantly lower than trips made during brooding (incubation 4·52 ± 0·50 SD W kg−1vs brooding 4·98 ± 0·55 SD W kg−1).

The rate of daily mass gain decreased significantly with time at sea during incubation whereas the rate of daily mass gain increased significantly with time at sea during brooding.

Foraging effort was higher during brooding, suggesting that birds were minimizing time at sea to maximize the rate of food delivery to chicks. In contrast, foraging effort was lower during incubation, suggesting that birds were maximizing time at sea and minimizing the energy costs of foraging.

Foraging costs were also different between sexes. However, this was related to body size differences and not to differences in foraging effort as suggested in previous studies.
Identification of receptors and Smad proteins involved in activin signalling in a human epidermal keratinocyte cell line
Authors: Shimizu Akira , Kato Mitsuyasu , Nakao Atsuhito , Imamura Takeshi , Ten Dijke Peter , Heldin Carl‐Henrik , Kawabata Masahiro , Shimada Shinji , Miyazono Kohei
Published: March 2003

Background:

Activin A is a multifunctional protein, which is a member of the transforming growth factor‐β (TGF‐β) superfamily. Smad proteins have recently been shown to transduce signals for the TGF‐β superfamily of proteins, and Smad2 was implicated in activin signalling in Xenopus embryos.

Results:

We identified the receptors and Smad proteins activated by activin A in a human epidermal keratinocyte cell line, HaCaT. The major activin receptors expressed on HaCaT cells were activin type II receptor (ActR‐II) and activin type IB receptor (ActR‐IB). We have also shown that in HaCaT cells, activin A induced the phosphorylation of Smad3 and, to a lesser extent, of Smad2. On the other hand, TGF‐β induced an efficient phosphorylation of both Smad2 and Smad3. Activin A preferentially induced the nuclear translocation of Smad3 in HaCaT cells, whereas TGF‐β strongly induced the nuclear translocation of Smad2, as well as other Smads. Moreover, a constitutively active form of ActR‐IB efficiently stimulated the formation of a heteromeric complex between Smad3 and Smad4 in COS cells transfected with Smad cDNAs.

Conclusions:

These results suggest that activin A binds to a receptor complex of ActR‐II and ActR‐IB, and preferentially activates Smad3 in HaCaT human keratinocytes.
Regulatory mechanisms in expression of the traY‐I operon of sex factor plasmid R100: involvement of traJ and traY gene products
Authors: Taki Keiko , Abo Tatsuhiko , Ohtsubo Eiichi
Published: March 2003

Background:

The plasmid R100 encodes tra genes essential for conjugal DNA transfer in Escherichia coli. Genetic evidence suggests that the traJ gene encodes a positive regulator for the traY‐I operon, which includes almost all the tra genes located downstream of traJ. The molecular mechanism of regulation by TraJ, however, is not yet understood. traY is the most proximal gene in the traY‐I operon. TraY promotes DNA transfer by binding to a site, sbyA, near the origin of transfer. TraY is suggested to have another role in regulation of the traY‐I operon, since it binds to two other sites, named sbyB and sbyC, located in the region preceding traY‐I.

Results:

Using a traY‐lacZ fusion gene, we showed that the traY‐I operon was expressed only in the presence of traJ. The TraJ‐dependent expression of traY‐I required the E. coliarcA gene, which encodes a host factor required for conjugation. TraJ‐dependent transcription occurred from a promoter (named pY) located upstream of traY‐I. The isolated TraJ protein was found to bind to a dyad symmetry sequence, named sbj (specific binding site of TraJ), which existed in the intergenic region between traJ and traY‐I. We also demonstrated that TraY repressed the TraJ‐dependent expression of traY‐I at the TraY binding sites, sbyB and sbyC, which overlapped with pY.

Conclusions:

TraJ is a protein which binds to the sbj site in the region upstream of the promoter pY and positively regulates expression of the traY‐I operon in the presence of the E. coliarcA gene. Since sbj is located 93 bp upstream of pY in the intergenic region between traJ and traY‐I, TraJ presumably contacts with a transcription apparatus to promote transcription from pY. TraY, which is known to activate the initiation of conjugal DNA transfer, has a new role in the transcriptional autoregulation of traY‐I expression. At levels which are sufficient to initiate conjugal DNA transfer, TraY represses traY‐I transcription in the presence of TraJ.
AMY‐1, a novel C‐MYC binding protein that stimulates transcription activity of C‐MYC
Authors: Taira Takahiro , Maëda Junko , Onishi Takako , Kitaura Hirotake , Yoshida Shu , Kato Hiroyuki , Ikeda Masako , Tamai Katsuyuki , M. Iguchi‐Ariga Sanae M. , Ariga Hiroyoshi
Published: March 2003

Background

The c‐myc proto‐oncogene has been suggested to play key roles in cell proliferation, differentiation, transformation and apoptosis. A variety of functions of C‐MYC, the product of c‐myc, are attributed to protein–protein interactions with various cellular factors including Max, YY1, p107, Bin1 and TBP. Max and YY1 bind to the C‐terminal region of C‐MYC, while p107, Bin1 and TBP bind to the N‐terminal region covering myc boxes. The N‐terminal region is involved in all the biological functions of C‐MYC, and different proteins are therefore thought to interact with the N‐terminal region of C‐MYC to display different functions.

Results

We cloned two cDNAs which encode a novel C‐MYC‐binding protein of 11 kDa, designated AMY‐1 (Associate of C‐MYC). The two cDNAs, AMY‐1L and AMY‐1S, derived from alternative usage of polyadenylation signals, code for the same protein of 11 kDa. AMY‐1 was bound via its C‐terminal region to the N‐terminal region of C‐MYC (amino acids nos 58–148) corresponding to the transactivation domain. AMY‐1 was localized in the cytoplasm in cells expressing c‐myc at low levels, but in the nucleus in the cells of a high c‐myc expression in transiently transfected cells. A similar difference in endogenous AMY‐1 localization was observed during the cell cycle: AMY‐1 translocated from cytoplasm to nucleus during the S phase when c‐myc expression was increased. AMY‐1 by itself did not recognize the E‐box element, the MYC/Max binding sequence, nor did it transactivate via the element, but stimulated the activation of E‐box‐regulated transcription by MYC/Max. FISH analyses revealed that the amy‐1 gene was located at 1p32.2–1p33 in human genome.

Conclusions

AMY‐1 is a 11 kDa protein which binds to the N‐terminal region of C‐MYC and stimulates the activation of E‐box‐dependent transcription by C‐MYC. AMY‐1, which mostly localizes in the cytoplasm, translocates into the nucleus in the S phase of the cell cycle upon an increase of c‐myc expression, and may thus control the transcriptional activity of C‐MYC.
Disruption of the midkine gene (Mdk) resulted in altered expression of a calcium binding protein in the hippocampus of infant mice and their abnormal behaviour
Authors: Nakamura Eishin , Kadomatsu Kenji , Yuasa Shigeki , Muramatsu Hisako , Mamiya Takayoshi , Nabeshima Toshitaka , Fan Qi‐Wen , Ishiguro Kazuhiro , Igakura Tadahiko , Matsubara Shuichiro , Kaname Tadashi , Horiba Mitsuru , Saito Hidehiko , Muramatsu Takashi
Published: March 2003

Background:

Midkine (MK) is a growth factor implicated in the development and repair of various tissues, especially neural tissues. However, its in vivo function has not been clarified.

Results:

Knockout mice lacking the MK gene (Mdk) showed no gross abnormalities. We closely analysed postnatal brain development in Mdk(–/–) mice using calcium binding proteins as markers to distinguish neuronal subpopulations. Intense and prolonged calretinin expression was found in the dentate gyrus granule cell layer of the hippocampus of infant Mdk(–/–) mice. In infant Mdk(+/+) mice, calretinin expression in the granule cell layer was weaker, and had disappeared by 4 weeks after birth, when calretinin expression still persisted in Mdk(–/–) mice. Furthermore, 4 weeks after birth, Mdk(–/–) mice showed a deficit in their working memory, as revealed by a Y‐maze test, and had an increased anxiety, as demonstrated by the elevated plus‐maze test.

Conclusion:

Midkine plays an important role in the regulation of postnatal development of the hippocampus.
Expression of the Vax family homeobox genes suggests multiple roles in eye development
Authors: Ohsaki Kanae , Morimitsu Toshiharu , Ishida Yoko , Kominami Ryo , Takahashi Naoki
Published: March 2003

Background

Homeobox gene products are thought to regulate target genes involved in the regional specification of tissues and organs. Several genes play roles in eye development.

Results

We isolated two new mouse homeobox genes, Vax1 and Vax2, expressed in retina primordium. The two genes share the same gene organization, consisting of three exons with predicted amino acid sequences identical in the homeodomain but diversified in other regions. At 9.5 days post coitum, both Vax genes were expressed in optic vesicles. At 11.5–14.5 dpc, Vax1 became restricted to the optic stalk, while Vax2 was expressed in the ventral half of the neural retina. Mapping of Vax2 between D6Mit3 and D6Mit8 on chromosome 6 indicated a possible linkage with Emx1.

Conclusions

The expression patterns of Vax genes suggest separate and specific involvement in eye development. Vax1 may contribute to differentiation of the neuroretina, pigmented epithelium and optic stalk, while Vax2 could function in the establishment of the dorso‐ventral axis of the retina and the visual system. The chromosomal location of Vax2 suggests that Vax2‐Emx1 and Vax1‐Emx2 arose by chromosome duplication of the same ancestral gene.
The role of HSP90 in evolution
Authors: Yahara Ichiro
Published: March 2003

A mechanism by which morphological mutations are stored without expressing phenotypes was unraveled by Rutherford & Lindquist (1998) through genetic studies of Hsp83 (HSP90) in Drosophila. Cryptic mutations are essentially neutral and therefore evolve in the absence of selective constraint. A shift from neutral mutations to selective mutations is induced when flies are exposed to environmental stress. This is a step toward understanding macroevolution in molecular terms.
Fission yeast APC/cyclosome subunits, Cut20/Apc4 and Cut23/Apc8, in regulating metaphase‐anaphase progression and cellular stress responses
Authors: Yamashita Yukiko M. , Nakaseko Yukinobu , Kumada Kazuki , Nakagawa Takashi , Yanagida Mitsuhiro
Published: March 2003

Background

The 20S cyclosome/APC complex promotes metaphase–anaphase transition by ubiquitinating its specific substrates such as mitotic cyclins and anaphase inhibitor Cut2/Pds1/securin. The complex has been shown to contain more than 10 proteins in budding yeast and frog. In fission yeast, however, only five (Cut4, Cut9, Nuc2, Apc10, Hcn1) have been identified.

Results

More than five hundred temperature‐sensitive mutants were screened for identifying those defective in mitotic anaphase. Fifty‐five showed the cut (cell untimely torn) phenotype or metaphase‐arrest phenotypes, 27 of them locating at new loci. Their extracts were run in sucrose gradient centrifugation, and four showed alterations in the sedimentation profiles. The gene products of cut20+ and cut23+ were thus identified. Phenotypes of cut20–100 mutant highly resemble cut4–533 in many ways: they are hypersensitive to canavanine and CdCl2, and suppressed by PKA‐inactivating regulators, cAMP‐dependent phosphodiesterase and PKA regulatory subunits. Cut20 interacts closely with Cut4 in the assembly process of cyclosome. But cut20 mutant differs from cut4, as a novel gene stw1+ suppresses cut20 mutant but not cut4. cut23–194 mutant cells are sterile and blocked at metaphase, but does not show sensitivity to the stress and cAMP. TPR repeat‐containing Cut23 may not be the stable component of APC/cyclosome, and its level significantly fluctuates during cell cycle. Cut23 may be ubiquitinated and degraded in a cell cycle dependent fashion.

Conclusions

We identified two new subunits of fission yeast cyclosome/APC complex. Our observations indicate that cyclosome components are divided into several subgroups with distinctly different roles.
Tuning of the porin expression under anaerobic growth conditions by His‐to‐Asp cross‐phosphorelay through both the EnvZ‐osmosensor and ArcB‐anaerosensor in Escherichia coli
Authors: Matsubara Masahiro , Kitaoka Shin‐ichi , Takeda Shin‐ichiro , Mizuno Takeshi
Published: March 2003

Background

Widespread bacterial signal transduction circuits are generally referred to as ‘two‐component systems’ or ‘histidine (His)‐to‐aspartate (Asp) phosphorelays.’ In Escherichia coli, as many as 30 distinct His‐to‐Asp phosphorelay signalling pathways operate in response to a wide variety of environmental stimuli, such as medium osmolarity and anaerobiosis. In this regard, it is of interest whether or not some of them together constitute a network of signalling pathways through a physiologically relevant mechanism (often referred to as ‘cross‐regulation’). We have addressed this issue, with special reference to the osmo‐responsive EnvZ and anaero‐responsive ArcB phosphorelay signalling pathways in E. coli.

Results

Under standard aerobic growth conditions, it is well known that the osmoregulatory profile of the outer membrane porins (OmpC and OmpF) is mainly regulated by the EnvZ‐OmpR phosphorelay system in response to medium osmolarity. In this study, it was found that, under anaerobic growth conditions, E. coli cells exhibit a markedly altered expression profile of OmpC and OmpF This profile was significantly different from that observed for the cells grown aerobically. Results from extensive genetic studies showed that, under such anaerobic growth conditions, the arcB gene encoding the anaero‐sensory His‐kinase appears to be an auxiliary genetic determinant that regulates the expression profile of porins. We then provided several lines of in vivo and in vitro evidence, which taken together, supported the following conclusions.

Conclusions

Under anaerobic growth conditions, porin expression is tuned not only by the authentic osmo‐resposive EnvZ sensor, but also by the anaero‐responsive ArcB sensor, in an OmpR‐dependent manner. It is suggested that such ArcB‐mediated cross‐regulation plays a physiological role by integrating anaerobic respiratory signals into the porin regulation in E. coli anaerobiosis. The proposed model is a clear example of the interplay of two distinct His‐to‐Asp phosphorelay signalling pathways.
Expression and characterization of nonmammalian selenoprotein P in the zebrafish,Danio rerio
Authors: Tujebajeva Rosa M. , Ransom David G. , Harney John W. , Berry Marla J.
Published: March 2003

Selenoprotein P is a protein of considerable intrigue, due to its unusual composition and requirements for its biosynthesis. Whereas most selenoproteins contain a single selenocysteine residue, the human, bovine and rodent selenoprotein P genes encode proteins containing 10–12 selenocysteines. Selenoprotein P genes have, to date, only been reported in mammals, and the function of the protein remains elusive.

Herein, we report the identification and characterization of nonmammalian selenoprotein P in the zebrafishDanio rerio. Sequencing of the cDNA revealed the presence of 17 selenocysteine codons, the highest number reported in any protein. Two histidine‐rich regions present in the mammalian selenoprotein P sequences are conserved in the zebrafish protein, and two SECIS elements are present in the 3′ untranslated region. Whole‐mountin situhybridization of zebrafish embryos revealed high levels of expression of selenoprotein P mRNA in fertilized eggs and in the yolk sac of developing embryos. Transient transfection of the cDNA in mammalian cells resulted in efficient expression of the full‐length secreted selenoprotein. A single N‐glycosylation site is predicted, and shown to be utilized.

Discovery of selenoprotein P in the zebrafish opens a previously unavailable avenue for genetic investigation of the functions of this unusual protein.
Ankycorbin: a novel actin cytoskeleton‐associated protein
Authors: Peng Ying‐Feng , Mandai Kenji , Sakisaka Toshiaki , Okabe Noriko , Yamamoto Yasunori , Yokoyama Shigekazu , Mizoguchi Akira , Shiozaki Hitoshi , Monden Morito , Takai Yoshimi
Published: March 2003

Actin cytoskeleton structures are essential for a wide variety of cell functions, including cell shape change, cell motility, cell adhesion, cell polarity and cytokinesis. Many actin filament (F‐actin)‐binding proteins have been isolated and implicated in the maintenance and reorganization of actin cytoskeleton structures.

We purified here a novel protein with a molecular mass of about 125 kDa (p125) from rat liver. We cloned its cDNA from a mouse kidney cDNA library and determined its nucleotide and deduced amino acid sequences. p125 was a protein of 979 amino acids with a calculated Mr of 108 847. p125 contained six ankyrin repeats in the N‐terminal region and a domain predicted to form a coiled‐coil structure in the C‐terminal region. We named p125 ankycorbin (ankyrin repeat‐ and coiled‐coil structure‐containing protein). Northern blot analysis indicated that ankycorbin was ubiquitously expressed in all the tissues examined. Immunofluorescence and immunoelectron microscope analyses revealed that ankycorbin was associated with the cortical actin cytoskeleton structures in terminal web and cell‐cell adhesion sites and stress fibres. However, ankycorbin did not directly bind to F‐actin as estimated by the F‐actin co‐sedimentation assay.

These results indicate that ankycorbin is indirectly associated with the actin cytoskeleton structures, presumably through an unidentified factor and suggest that it is involved in their maintenance and/or reorganization.
Two proteins, YfiA and YhbH, associated with resting ribosomes in stationary phase Escherichia coli
Authors: Maki Yasushi , Yoshida Hideji , Wada Akira
Published: March 2003

Ribosomes in Escherichia coli change their composition and conformation in the stationary phase. Ribosome modulation factor (RMF) and ribosomal protein S22 are known to be associated with stationary phase ribosomes. RMF association causes the loss of translational activity and the dimerization of 70S ribosomes into 100S ribosomes, which may increase cell survival in the stationary phase.

Two weakly acidic proteins having related amino acid sequences were found to be associated with E. coli ribosomes in the stationary phase. These proteins are the products of ORFs named yfiA and yhbH. The sum of the copy numbers of their product proteins, YfiA and YhbH, in the ribosomal particles was low in the log phase, but increased to nearly one in the stationary phase. YfiA was found in the 70S ribosomal fraction rather than the 100S. On the other hand, YhbH was detected exclusively in the 100S ribosomal fraction. When the stationary phase cells were transferred to fresh medium, YfiA and YhbH were found in the 70S ribosomal fraction, but not in the polysome fraction.

Two proteins, YfiA and YhbH, associated with E. coli ribosomes were found to accumulate in the stationary phase, leading to the formation of several types of ribosomes. They are not likely to have roles in the elongation step of the translation in log phase cells, but are likely to be involved in the stabilization and preservation of ribosomes in the stationary phase, which might be necessary for cell survival.
Human homologues of the Caenorhabditis elegans cell polarity protein PAR6 as an adaptor that links the small GTPases Rac and Cdc42 to atypical protein kinase C
Authors: Noda Yukiko , Takeya Ryu , Ohno Shigeo , Naito Seiji , Ito Takashi , Sumimoto Hideki
Published: March 2003

Background

Asymmetric cell division in the Caenorhabditis elegans embryos requires products of par (partitioning defective) genes 1–6 and atypical protein kinase C (aPKC), whereas Cdc42 and Rac, members of the Rho family GTPases, play an essential role in cell polarity establishment in yeast and mammalian cells. However, little is known about a link between PAR proteins and the GTPases in cell polarization.

Results

Here we have cloned cDNAs for three human homologues of PAR6, designated PAR6α, β and γ, comprising 345, 372 and 376 amino acids, respectively. The PAR6 proteins harbour a PDZ domain and a CRIB‐like motif, and directly interact with GTP‐bound Rac and Cdc42 via this motif and with the aPKC isoforms PKCι/λ and PKCζ via the N‐terminal head‐to–head association. These interactions are not mutually exclusive, thereby allowing the PAR6 proteins to form a ternary complex with the GTPases and aPKC, both in vitro and in vivo. When PAR6 and aPKC are expressed with a constitutively active form of Rac in HeLa or COS‐7 cells, these proteins co‐localize to membrane ruffles, which are known to occur at the leading edge of polarized cells during cell movement.

Conclusion

Human PAR6 homologues most likely play an important role in the cell polarization of mammalian cells, by functioning as an adaptor protein that links activated Rac and Cdc42 to aPKC signalling.
Down‐regulation of α6 integrin, an anti‐oncogene product, by functional cooperation of H‐Ras and c‐Myc
Authors: Fujimoto Hiroko , Tanaka Yoshiya , Liu Zhao‐Jun , Yagita Hideo , Okumura Ko , Kosugi Atsushi , Morinobu Akio , Umehara Hisanori , Yamamura Hirohei , Minami Yasuhiro
Published: March 2003

Background

The molecular basis of cooperation of H‐Ras and c‐Myc in regulating cellular behaviour, such as cell adhesiveness, is still poorly understood. To investigate the role of H‐Ras and c‐Myc in cell adhesiveness, a constitutively active H‐RasV12 (H‐RasV12) and c‐Myc were stably expressed, singly or in combination in a haematopoietic cell line, and the expression and activity of cell adhesion molecules were monitored.

Results

We have shown that the ectopic expression of H‐RasV12, but not c‐Myc alone, in a haematopoietic cell line, induces the activation of very late antigen‐6 (VLA‐6, α6β1) integrin. Co‐expression of H‐RasV12 and c‐Myc in the same cells further resulted in the induction of expression of vascular cell adhesion molecule‐1 (VCAM‐1) and the inhibition of expression of α6 integrin, a candidate anti‐oncogene product, leading to a loss of adhesiveness to laminin (Lm), a ligand for VLA‐6.

Conclusions

Cooperation of H‐Ras and c‐Myc reciprocally regulates expression of the adhesion molecules, α6 integrin and VCAM‐1. Our results represent an unprecedented account of the cooperation of the oncogene products, H‐Ras and c‐Myc, to inhibit expression of an anti‐oncogene product, α6 integrin.
Distribution of phosphorylated glial fibrillary acidic protein in the mouse central nervous system
Authors: Takemura Masaaki , Nishiyama Hiroshi , Itohara Shigeyoshi
Published: March 2003

Background: Glial fibrillary acidic protein (GFAP) is the principal component of intermediate filaments (IFs) in mature astrocytes in the central nervous system (CNS). Like other IF proteins, GFAP has multiple phosphorylation sites in the N‐terminal head domain. The distribution of phospho‐GFAP in vivo has not been elucidated.

Results: We generated Gfaphwt knock‐in mice, in which the coding region for the head domain of GFAP is replaced with the corresponding human sequence. In combination with a series of monoclonal antibodies (mAbs) reactive to human phospho‐GFAP, we visualized the distribution of phospho‐GFAP in vivo in mice. GFAP phosphorylated at Thr7, Ser8 and/or Ser13 increased postnatally in the CNS of these mice. Limited populations of GFAP‐positive astrocytes were labelled with anti‐phospho‐GFAP mAbs in most brain areas, whereas almost all the astrocytes in the optic nerve and spinal cord were labelled. Astrocytes in the subventricular zone and rostral migratory stream preferentially contained phospho‐GFAP. In a cold injury model of the cerebral cortex, we detected phospho‐GFAP in reactive astrocytes at 2–3 weeks after the injury.

Conclusions: Phospho‐GFAP provides a molecular marker indicating the heterogeneity of astrocytes, and Gfaphwt knock‐in mice will aid in monitoring intracellular conditions of astrocytes, under various conditions. Our results suggest that the phosphorylation of GFAP plays a role in non‐dividing astrocytes in vivo.