bluuebunny/crossref_metadata_2025 huggingface dataset:
Controlled atmospheres and sugar can delay malate synthase gene expression during asparagus senescence
Authors: Coupe Simon A. , Sinclair Ben K. , Somerfield Sheryl D. , Hurst Paul L.
Published: September 2002

A cDNA clone encoding malate synthase (MS; EC 4.1.3.2) was isolated from a 48-h postharvest asparagus (Asparagus officinalis L.) spear cDNA library using a MS clone from Brassica napus. The asparagus MS (AoMS1) cDNA hybridized to a 1.9-kb transcript that increased in abundance preferentially in spear-tip tissue during postharvest storage. The AoMS1 transcript also accumulated during natural foliar senescence of asparagus fern. The cDNA consists of 1960 nucleotides with an open reading frame of 1665 nucleotides or 555 amino acids, and encodes a deduced protein with a predicted Mr of 63 kDa and a pI of 8.1. The deduced amino acid sequence of AoMS1 showed high identity with the B. napus MS clone (77.2%) used to isolate it, and with MS from cucumber (77%). Genomic Southern analysis suggests that a single gene in asparagus encodes AoMS1. Controlled- atmosphere treatments aimed at reducing deterioration of harvested asparagus spears reduced the expression of AoMS1. The reduction was correlated with the reduced oxygen level, and reduced MS enzyme activity was also observed. Asparagus cell cultures were used to test the role of sugar status in regulating AoMS1 gene expression. In cultures without sucrose there was an accumulation of AoMS1 transcript that was absent in cultures containing sucrose.
Prolonged exposure to ethylene stimulates the negative gravitropic responses of Arabidopsis inflorescence stems and hypocotyls
Authors: Lu Bingwen , Yu Ho Yan , Pei Lai Kwan , Wong Man Yu , Li Ning
Published: September 2002

The actual effect of ethylene on shoot gravitropic response has been controversial. To elucidate the role of ethylene in the modulation of shoot gravitropic response, Arabidopsis inflorescences and light-grown seedlings were pretreated with 0.1-10 -1 of ethylene for either a long (12-48 h) or short term (0.5 h). When the gravicurvature was measured either in air or in ethylene, it was found that prolonged exposure to various levels of ethylene stimulated both inflorescence stem and hypocotyl gravicurvature in air, while the continued presence of ethylene immediately following reorientation of plant tissues inhibited gravicurvature of both tissues. Both stimulatory and inhibitory effects existed in inflorescence stems and hypocotyls when the plant tissues were exposed to a chosen concentration of ethylene. Stimulation by ethylene was stronger than its inhibition in inflorescence stems, while the reverse was true for the hypocotyls. Therefore, the continued presence of high levels of naturally produced ethylene in eto1-1 did not suppress the faster gravicurvature of inflorescence stems, whereas the removal of exogenously applied ethylene was necessary to observe faster gravicurvature of both the wild-type and eto1-1 hypocotyls. Both effects acted through the known ethylene receptor complex. These results strongly suggest that ethylene of a chosen concentration has opposing effects on the negative gravitropic responses of both inflorescence stems and hypocotyls. The ultimate negatively gravitropic behaviour of a plant tissue, when exposed to ethylene, depends on the dynamic interplay between these two opposing effects.
The ascorbic acid cycle mediates signal transduction leading to stress-induced stomatal closure
Authors: Maggio Albino , McCully Michael G. , Kerdnaimongkol Kanogwan , Bressan Ray A. , Hasegawa Paul M. , Joly Robert J.
Published: September 2002

Using a combination of pharmacological approaches, mutation analysis and a gene silencing strategy, we present evidence that treatment of tomato (Lycopersicon esculentum Mill.) plants with exogenous ascorbate (AsA) subsequently increases the level of cellular AsA and causes stomatal closure. Using the ABA-deficient mutants flacca and sitiens, we show that the AsA-mediated induction of stomatal closure requires the participation of ABA. In addition, ABA acts independently of its role in mediating another stress response, proline accumulation. Because cellular AsA level was not elevated during stomatal closure, we hypothesized that stomatal closure relies on the activation of the AsA cycle and possible accumulation of intermediate components, such as monodehydroascorbate, that have been reported to be involved in mediating stress-induced responses. To establish a link between H2O2 production, the AsA cycle and stomatal closure, we also evaluated the effect of AsA treatment on catalase-deficient transgenic plants, which have a constitutively high level of H2O2. Interestingly, stomata of catalase-deficient plants were much more responsive to AsA treatment, compared with wild-type control plants. Because an increase in cellular H2O2 upon stress has been widely documented in many organisms and has been interpreted as a signal that initiates a cascade of stress-induced responses, we suggest that stress-induced stomatal closure is mediated by H2O2 and activation of the AsA cycle.
Temperature dependence of guard cell respiration and stomatal conductance co-segregate in an F2 population of Pima cotton
Authors: Lu Zhenmin , Quiñones Miguel A. , Zeiger Eduardo
Published: September 2002

In Pima cotton
(Gossypium barbadense L.), stomatal conductance shows a
strong response to temperature. At high temperature (40˚C), the stomatal
conductance of greenhouse- and growth chamber-grown leaves is three and four
times higher than that measured at lower temperature (25ºC),
respectively. The segregation of stom-atal conductance observed in an
F2 population obtained from a cross between a primitive
cotton (B368) and a modern Pima line (Pima S-6) increased substantially with
temperature in both light and darkness. Furthermore, F2 segregants with high
stomatal conductance at high temperature were more sensitive to temperature,
showing larger changes in conductance in response to an increase in
temperature when compared to F2 segregants having low
stomatal conductance. Rates of guard cell respiration measured in
enzymatically-cleaned epidermal peels, mechanically isolated from the same
F2 plants, showed the same temperature dependence. The
temperature-induced respiration enhancement was higher in guard cells with
high respiration rates. There were positive correlations between stomatal
conductance and guard cell respiration rates, and between stomatal conductance
and the sensitivity of respiration to changes in temperature. These results
imply that guard cell respiration and stomatal conductance co-segregate in
Pima cotton plants, suggesting that guard cell respiration is a component of
the sensory transduction pathway controlling stomatal responses to
temperature.
Photosynthetic acclimation to high light conditions in mature leaves of Coffea arabica L.: role of xanthophylls, quenching mechanisms and nitrogen nutrition
Authors: Ramalho José C. , Pons Thijs L. , Groeneveld Henri W. , Azinheira Helena G. , Nunes M. Antonieta
Published: September 2002

Young coffee plants (Coffea arabica L. cv.
Catuaí), originally from a shaded habitat, were separated in three
groups to be grown under different levels of N fertilization: 0.3 mmol N
supplements were given to the soil every 7 days (high N treatment, 2N), every
15 days (medium N treatment, 1N) and every 45 days (low N treatment, 0N).
These plants were later exposed to a high sunlight irradiance (noon PPFD up to
1500 µmol m–2
s–1 ) for a period of 12 or 15 days. Among others,
the values of electron trans-port capacity, maximum carboxylation activity,
photosynthetic capacity (Amax) and
several fluorescence parameters
(Fv/Fm,
Fv´/Fm´,
qP, &phis;e) first showed a
reduction (until the 4th–7th day) in all N treatments, followed by an
N-dependent recovery. The 2N plants were less affected in the first few days
and, at the end of the stress period, showed a better recovery for most of the
studied parameters and the highest increase in the saturating PPFD for net
photosynthesis and A max . The
present work shows that the ability to acclimate displayed by the mature
leaves of 2N plants was accompanied by an increase in energy dis-sipation
mechanisms. These include an increase in the ‘high energy’
quenching and, mostly, the presence of higher contents of some xanthophylls
(zeaxanthin and lutein) and carotenes, which helped to decrease the energetic
overcharge in the photosystems. Pigment changes in mature leaves suggest that
N can promote specific mechanisms of acclimation others than those that might
be expected from a preferential partition of the element N into photosynthetic
components.
Variation in puroindoline polypeptides in Australian wheat cultivars in relation to grain hardness
Authors: Turnbull Kym-Marie , Gaborit Therese , Marion Didier , Rahman Sadequr
Published: September 2002

The sequence of the puroindoline-b gene from 15 Australian wheat cultivars was
determined. Sequence variation was observed in the WPTKWWKGGCE motif of the
deduced puroindoline-b protein sequence. Previously, it has been suggested
that this sequence is crucial in determining grain hardness. In this study, no
correlation was found between the variation in this sequence and the hardness
or softness of the cultivar. The amounts of puroindo-line- a and
puroindoline-b protein in a selection of hard and soft Australian wheat
cultivars were also determined using ELISA techniques. Both soft and hard
cultivars had variable amounts of puroindoline-a and puroindoline-b. In
particular, it is notable that the hard cultivars Cook and Diaz contained high
amounts of puroindoline-a and puroin-doline- b and also contained the
puroindoline-b sequence previously reported to be associated with grain
softness. These results suggest that if the puroindoline proteins are involved
in determining grain softness or hardness they do so as part of a
multi-component mechanism.
A novel class of fast electrical events recorded by electrodes implanted in tomato shoots
Authors: Pickard William F.
Published: September 2002

An unfamiliar class of electrical events with rapid rise and slow decay has
been identified in tomato (Lycopersicon esculentum
Mill.) plants impaled by metal electrodes. Rise-times of these extracellularly
detected events can be 200 µs or less, while fall-times can require
hundreds of milliseconds. In excised tomato shoots, these events are
associated with the imposition of water stress. The hypothesized origin of
these events is the fracture of water columns in the xylem and the
triboelectrification that occurs as the ends of the columns snap apart.
Factors affecting the relationship between carbon isotope discrimination and transpiration efficiency in blue oak (Quercus douglasii)
Authors: Matzner Steven L. , Rice Kevin J. , Richards James H.
Published: September 2002

In a greenhouse study, variation in plant and leaf transpiration efficiency(W, A/E)and carbon isotope discrimination (D) were assessed forQuercus douglasii Hook & Arn. (blue oak) from a‘wet’ (930 mm) and a ‘dry’ (500 mm) site. Plants weregrown at 75–100% (wet) and 50–75% (dry) of fieldcapacity. Family variation masked population level differences, and twocontrasting patterns emerged. The expected pattern was observed with drytreatment plants having lower leaf internal CO 2concentration (c i ) and D, andhigher W andA/E. For families with verylarge increases in plant size from dry to wet treatments, however, wettreatment plants had lower c i andD, and higher W andA/E, reflecting a greaterinfluence of the maximum assimilation rate (Amax ) compared with stomatal conductance(g s ) on ci . In addition, large within-population variation inplant size appears to have affected both n (the vapor pressure deficit) andø c (a measure of respiredcarbon). Lower n for large plants may be due to the higher rates of stomatalconductance and greater leaf cooling. Values of øc appear to have increased for plants below 2.5 g (drymatter, DM). Variation in these factors would directly affect the relationshipbetween W and D. This study illustrates a case where significant within-population variation can occur in the relative effect ofg s and Amax on c i .In addition this study indicates that øc may not be a constant for a species.
Effects of UV-C irradiation on lipid peroxidation markers during ripening of tomato (Lycopersicon esculentum L.) fruits
Authors: Barka Essaid Ait , Kalantari Siamak , Makhlouf Joseph , Arul Joseph
Published: September 2002

The effects of a hormic dose (3.7 kJ m−2) of UV-C
(254 nm) on changes in fruit membrane lipids perox-idation markers during
storage were determined using tomato
(Lycopersicon esculentum L. cv. Trust) fruit. There were
two distinct response phases following the treatment. A significant induction
of lipid peroxidation markers (lipofuscin-like compounds, malondialdehyde,
aldehydes, pentane, ethane, hydrogen peroxide, and efflux of elec-trolytes
including potassium and calcium) occurred within the first 5 days. This
induction suggests that the cell mem-brane was the primary target of UV-C
irradiation. After this period, the level of all of these peroxidation markers
become lower in UV-C-treated fruit than in control fruit, suggesting the
induction of a defense or repair mechanism, probably involving production of
antioxidants and activation of antioxidative enzyme. Within the second phase,
any changes in lipid peroxidation activity reflected the fruit ripening /
senescence process rather than the UV-C effect.
Phosphate absorption by Arabidopsis thaliana: interactions between phosphorus status and inhibition by arsenate.
Authors: Clark Gregory T. , Dunlop James , Phung H. Thai
Published: September 2002

The effects of phosphorus status and arsenate on the absorption of phosphate
by roots of intact sterile seedlings of
Arabidopsis thaliana were studied by analysing the rate
of depletion of phosphate from solutions initially containing 10 M
KH2PO4. Depletion of phosphate
from the experimental solutions was measured both chemically and by labelling
with 32P. There was a substantial efflux of phosphate
coincident with a rapid influx of phosphate, with efflux increasing with
increasing phosphorus status. The highest rates of absorption were obtained
for the plants initially grown with a high level of phosphorus but then
deprived of phosphate for 5 d prior to the experiments, with the next highest
rates obtained for the most phosphorus-deficient plants. Kinetic analysis
suggests that changes in both the affinity and capacity of the absorption
mechanism contribute to differences in the rate of phosphate influx between
plants of different phosphorus status. Arsenate as 20 M
KH2AsO4 inhibited phosphate influx
in a manner such that all plants, regardless of their phosphorus status, had
the same phosphate influx rate. This was reflected in identical values for the
Michaelis constant, Km, and
maximum velocity as used in Michaelis–Menten kinetics,
Vmax. Arsenate had its greatest
effect on phosphate movement to the shoot. The simultaneous elimination of
differences in phosphate influx between plants of different phosphorus status
suggest that phosphate movement to the shoot may be important in the
regulation of influx by phosphorus status.
Photosynthetic characteristics of 10 Acacia species grown under ambient and elevated atmospheric CO2
Authors: Evans John R , Schortemeyer Marcus , McFarlane Nola , Atkin Owen K
Published: September 2002

Ten contrasting Acacia species were grown in glasshouses
with normal ambient CO2 or ele-vated to 700 µL
L–1. Plants were grown in sand with a complete
nutrient solution, including 5 mМ nitrate. Our objective was to determine
the degree to which photosynthesis, and the efficiency of nitrogen and water
use, were affected by growth under elevated CO2 in
contrasting plant species that differ in specific foliage area (foliage area
per unit foliage dry mass). Photosynthetic characteristics were measured at
several stages. Growth and measurement of gas exchange under 700 mL
L–1 CO2 resulted in enhanced
rates of CO2 assimilation per unit foliage area in nine
of the species. The degree of enhancement was independent of specific foliage
area. The exception was the slow-growing A. aneura,
which had lower rates of CO2 assimilation when grown and
measured at 700 µL L–1
CO2 compared to plants grown and measured at 350
µL L–1 CO2, at 50, 78
and 93 d after transplanting. Leaf conductance was reduced by growth in
elevated CO2 in only six of the species. Overall,
elevated CO2 improved the ratio of
CO2 assimi-lation to conductance by 78% and
increased CO2 assimilation per unit of foliage nitrogen
by 30% at a given specific foliage area. Detailed study of
A. saligna and A. aneura revealed
that the effects of the CO2 treatment were similarly
evident on all fully expanded phyllodes, regardless of their age.
Intercellular CO2 response curves were analysed on four
species and revealed no change in the ratio of electron transport to Rubisco
activities. However, for A. aneura and
A. melanoxylon, both electron transport and Rubisco
activities were reduced per unit foliage nitrogen, by growth under elevated
CO2 . For A. saligna and
A. implexa, these activities per unit nitrogen, were not
altered by the elevated CO2 treatment. To relate
CO2 assimilation rates to net assimilation rates (dry
matter increment per unit foliage area per day) derived from growth analysis,
between 30 and 50% of daily photosynthesis appeared to be consumed in
respiration. This proportion was not altered by CO2
treatment for seven of the Acacia species, but appeared
to be reduced in the other three. The increase in CO2
assimilation rate by growth under 700 com-pared to 350 µL
L–1 CO2 that was measured
(26%, mean of all species from two surveys), matched the increase in
net assimilation rate that had been derived from destructive sampling
(30%). We conclude that the increase in CO2
assimilation rate in the selected Acacia species was
independent of species, growth rate and foliage area per unit foliage dry
mass.
Phosphoenolpyruvate carboxylase during grape berry development: protein level, enzyme activity and regulation
Authors: Diakou Paraskevi , Svanella Laurence , Raymond Philippe , Gaudillère Jean-Pierre , Moing Annick
Published: September 2002

The protein level and regulation of
phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31,
involved in malic acid synthesis) was studied during the fruit development of
two grape (Vitis vinifera L.) varieties, ‘Cabernet
Sauvignon’ and ‘Gora Chirine’, with berries of normal and
low organic acid content, respectively. The protein level and
in vitro activity were higher in the low-acid variety
than in the normal-acid variety for most stages. In vivo
PEPC activity, measured using 14
CO2 labelling, was significantly higher in the low-acid
variety than in the normal-acid variety about 1 week before and 1 week after
veraison (the day which corresponds to the onset of ripening). However,
partitioning into malate was the same for both varieties. Antibodies raised
against the N-terminal part of
SorghumPEPC recognised the grape berry PEPC, indicating
the presence of the consensus phosphorylation site involved in PEPC
regulation. PEPC phosphorylation status was estimated by studying sensitivity
to pH and malate. Grape berry PEPC appeared more sensitive to low pH and
malate during ripening (IC50 malate, 0.2–0.7 mM)
compared to during the earlier stages of development
(IC50 malate, 1.2–2 mM) for both varieties.
Therefore, in the normal-acid variety, PEPC seems to participate in
controlling malic acid accumulation but does not seem to control the
differences in malic acid concentration observed between the two varieties.
The bigger picture - phloem seen through horticultural eyes
Authors: Bieleski Rod L.
Published: September 2002

Horticulturalists manipulate phloem transport
to achieve horticulturally-desirable results. The resulting crop behaviour can
help show how phloem works. In apple, the use of dwarfing rootstocks and
pruning management has greatly increased fruit sink capacity at the expense of
root and shoot sinks. Annual fruit yield can exceed100 t ha
–1 and account for 65% of total
photosynthate. If photosynthetic capacity exceeds fruit sink capacity, there
can be either a feedback reduction in photosynthesis, or accumulation of
phloem sugars in the fruit apoplast. In sugarcane, the sink is a linear body
encasing the full length of the phloem strands from leaf to root. Lateral
unloading must occur along the full length of the phloem. Unloading or loading
may occur in the same segment of phloem depending on conditions. In the
ornamental lily and daylily, the developing flower bud is a powerful sink,
doubling in dry weight each 48 h in the week of development from small bud to
opening. Once the flower is open, the phloem changes rapidly from unloading
behaviour as the tepals become vigorous exporters. The change in behaviour may
be coupled with processes mediating senescence and cell death. Implications to
phloem function are discussed.
Consequences of the expression of a bacterial glucokinase in potato tubers, both in combination with and independently of a yeast-derived invertase
Authors: Fernie Alisdair R. , Riesmeier Jörg W. , Martiny Annette , Ramalingam Sathishkumar , Willmitzer Lothar , Trethewey Richard N.
Published: September 2002

This paper originates from a presentation at the International Conference on Assimilate Transport and Partitioning, Newcastle, NSW, August 1999
The aim of this work was to further define the metabolic factors that regulate
carbohydrate metabolism in potato (Solanum tuberosum L.
cv. Desiree) tubers. We previously found that glycolysis is induced (and
starch accumulation reduced) in transgenic tubers in which a yeast invertase
and a glucokinase from Zymomonas mobilis were expressed
in the cytosol, whereas potato tuber size is dramatically increased when
invertase expression is targeted to the apoplast. In this study we describe
the further characterisation of potato tubers expressing a yeast invertase in
the apoplast. We also report the generation of two novel transgenic plants in
which the Z. mobilis glucokinase gene is expressed
tuber-specifically (either in the wild type or apoplastic invertase-expressing
back-ground). We evaluated the influence that increasing the glucokinase
activity, independent of invertase activity, had on the shift in carbon
partitioning, and assessed if the hexoses produced by the apoplastic cleavage
of sucrose could be brought into metabolism. We found that expression of
glucokinase either in the wild type or in the apoplastic invertase-expressing
background led to changes in the levels of glucose and glucose 6-phosphate.
However, these changes had little effect on carbon partitioning or tuber size
with respect to the parent line. We conclude that neither the accumulation nor
the phosphorylation of glucose play a pivotal role in the regulation of
metabolism or morphology in the potato tuber.
Tissue distribution of primary metabolism between epidermal, mesophyll and parenchymatous bundle sheath cells in barley leaves
Authors: Koroleva Olga A. , Tomos A. Deri , Farrar John , Roberts Peter , Pollock Christopher J.
Published: September 2002

This paper originates from a presentation at the International Conference on Assimilate Transport and Partitioning, Newcastle, NSW, August 1999
In order to investigate the roles of different cell types, metabolite
compartmentation in barley (Hordeum vulgare L.) leaf
tissue was mapped at the single-cell level, using single-cell sampling and
analysis (SiCSA) techniques. The partitioning of recently fixed
photoassimilate was investigated for the first time at single-cell resolution,
using BAMS (biological accelerator mass spectroscopy) for precise measurement
of 14C in femtomole quantities. The data obtained by
BAMS qualitatively reflect concentrations of sugars in different cell types
measured by SiCSA. Calculation of 14C-specific
activities showed that the radioactive label saturated the mesophyll and
parenchymatous bundle sheath (PBS) pools within the 45-min labelling period.
During the photoperiod, sucrose concentration increased to 200 mM in mesophyll
cells. The concentration of malate also increased during the photoperiod in
mesophyll and PBS cells. Epidermal cells contained very low concentrations of
sugar but high concentrations of malate (120–180 mM) and did not show
significant diurnal changes. Accumulation of sugars and fructan synthesis
could be induced in mesophyll and PBS cells by reduced export of sugars from
leaves or, alternatively, when sugars were supplied from excised leaf blade
bases immersed in a sucrose solution in the dark. The epidermis accumulated
additional malate in step with the accumulation of sugar by the
mesophyll/PBS cells during the long-term reduction of export.
Immunolocalisation of Rubisco and cytochrome oxidase proteins was used to
analyse the distribution of enzymes of photoassimilation and respiration
between functionally different cells in mature leaves of barley.
Fetal organ growth in response to oesophageal infusion of amniotic fluid, colostrum, milk or gastrin-releasing peptide: a study in fetal sheep
Authors: Trahair Jeff F. , Sangild Per T.
Published: September 2002

The hypothesis of the present study was that the infusion of the biological
fluids to which the develop-ing gut is normally exposed (i.e. amniotic fluid,
colostrum, milk) and a single growth factor (gastrin-releasing peptide), which
is found in high concentrations in fetal fluids and milk, could ameliorate the
altered growth induced by the elimination of swallowed input secondary to
ligation of the oesophagus. At 108–110 days of gestation the fetal
oesophagus was ligated and a catheter inserted towards the stomach (32
fetuses). At 117–119 days of gestation saline (n
= 5), amniotic fluid (n = 5), colostral
whey (n = 5), milk whey
(n= 5) or gastrin-releasing peptide (3.6 nmol day
–1 , n = 6), was
infused for 7 days (4 ¥ 20mL day –1 ), or no
infusion was given (ligated group, n = 6). A
further 15 fetuses ere not ligated (normal group, n
= 15). All fetuses had carotid artery and/or jugular vein catheters
implanted. At 124–126 days of gestation the fetus was delivered and
fetal body and organ weights recorded. Analysing the results by ANOVA, there
were no effects of either ligation alone or infusion after ligation on fetal
weight, crown–rump length, or weight relative to bodyweight of heart,
adrenal, pancreas, large intestine and cecum. There were significant
differences between the infusion groups for lungs, kidney, pancreas, total
gut, abomasum, small intestine, spleen, chest and neck thymus, and mesenteric
lymph nodes. Ligation alone significantly reduced small intestinal growth and
increased kidney and spleen growth. Colostrum infusion enhanced growth of most
organs. Gastrin-releasing peptide significantly increased growth of all the
immune organs studied. It was concluded that at an age when premature delivery
could be encountered, the fetal gut is capable of significant adaptive growth,
to varying degrees, depending on the enteral diet. Growth effects in organs
distant to the gut suggest that either gastrointestinal uptake and transport
of growth factors or altered nutrient uptake and/or availability can
affect the growth of other major fetal organs.
Regulation of early embryo development: functional redundancy between cyclin subtypes
Authors: Winston Nicola , Winston Nicola
Published: September 2002

Cellular proliferation during early embryo development is achieved by the
serial cleavage of individual blastomeres into increasingly smaller cells, in
the absence of cell growth. This simplified cell division process has
facilitated the study of the cell cycle and its regulatory pathways. The cell
cycle of mammalian cells is controlled by a number of mechanisms, including
the activity of cyclin-dependent protein kinase complexes. Numerous cyclin
proteins have been identified and these share structural and functional
characteristics. For each of the A- and B-type cyclins, two subtypes have been
identified so far in mammals. However, in both cases the two subtype genes are
expressed differentially, suggesting that they might have specific roles. The
requirement for individual cyclin A and B proteins during early mouse embryo
development has been examined using gene-targeted deletion and
immunofluorescence techniques. These studies have shown that cyclin A1 is not
essential for early embryonic development and cyclin A2 only becomes essential
for development beyond the stage of implantation. Cyclin B1 is also essential
for development and its critical regulatory role during the meiotic maturation
of mouse oocytes will be considered. This review will discuss the studies that
have attempted to explain the possible redundancy between the different cyclin
subtypes.
Ovarian tissue cryopreservation for cancer patients: who is appropriate?
Authors: Seymour John F.
Published: September 2002

In recent decades there has been parallel progress in the fields of cancer
chemotherapy and reproductive medicine technology, which has led to increasing
numbers of women surviving their malignancies, often with significant
reproductive impairment, and a range of choices for the potential preservation
of fertility, including storage of embryos, mature oocytes, immature oocytes
or ovarian tissue. Although each of these procedures has specific relative
advantages and disadvantages, there are no clear guidelines for selection of
patients for such interventions. There are six distinct issues that should be
considered before making any recommendations regarding the appropriateness of
any of the range of measures aimed at enhancing the future reproductive
capacity of the patient: (1) the risk of sterility with
the proposed treatment program; (2) the overall
prognosis for the patient; (3) the potential risks of
delaying chemotherapy; (4) the impact of any future
pregnancy upon the risk of tumour recurrence; (5) the
impact of any required hormonal manipulation on the tumour itself; and
(6) the possibility of tumour contamination of the
harvested tissue. For illustrative purposes, it is reasonable to assume that
the preservation of future fertility is likely to be a priority for women
under the age of 40 years. Within this group in 1996 in the Australian State
of Victoria (total population, ˜4.6 million), there were 837 cases
of cancer diagnosed (annual incidence rate, ˜60 per 100 000
population). Of those afflicted, it is estimated that 10% were
pre-pubertal, 38% were treated by potentially curative surgery alone,
15% had cancers of the reproductive tract, and 5% were treated
with palliative intent. Thus the remaining 32% of patients with
invasive cancer in this age group (267 per year) are potentially curable, and
require initial treatment, including chemotherapy. These tumours comprise
predominantly breast cancer (161 cases or 19%), sarcomas of bone and
soft-tissue (32 cases or 4%), and the haematologic malignancies
(Hodgkin’s disease, non-Hodgkin’s lymphomas, and the leukaemias,
each approximately 25 cases or 3%). Consideration of procedures that
may preserve future fertility would be appropriate in this group of patients.
Current data relating to the six issues noted earlier using contemporary
treatment programmes will be presented and discussed as they apply to each of
these categories of patient. An understanding of the relative importance of
each of these factors to patients with a range of malignancies will facilitate
the safe and appropriate application of the available methods to maintain the
possibility of future child-bearing.
Lineage specific differentiation of pluripotent cells in vitro: a role for extraembryonic cell types
Authors: Rathjen J. , Dunn S. , Bettess M. D. , Rathjen P. D.
Published: September 2002

The controlled differentiation of pluripotent cells will be a prerequisite for
many cell therapies. We have previously reported homogeneous conversion of
embryonic stem (ES) cells in vitro to early primitive
ectoderm-like (EPL) cells, equivalent to early primitive ectoderm, an
obligatory differentiation intermediate between ES cells and somatic cell
populations. Early primitive ectoderm-like cells differentiated within
aggregates form mesodermal lineages at the expense of ectoderm. In this work
we demonstrate that the failure of EPL cells to form ectodermal cell types
does not reflect an inherent restriction in developmental potential. Early
primitive ectoderm-like cells form ectodermal derivatives such as neurons in
response to neural inducers such as retinoic acid, or when differentiated in
the environment provided by ES cell embryoid bodies. This could be explained
by signals from the extraembryonic cell type visceral endoderm which forms in
differentiating ES cell but not EPL cell aggregates. Consistent with this
possibility, culture of EPL cell aggregates in the presence of visceral
endoderm-like signals did not prevent differentiation of the pluripotent
cells, but resulted in suppression of mesoderm formation. These results
suggest a role for visceral endoderm in regulation of germ layer specification
from pluripotent cells, and can be integrated into a model for cell
differentiation in vitro and
in vivo.
Ovarian responses in gonadotrophin-releasing hormone-treated anoestrous ewes: follicular and endocrine correlates with luteal outcome
Authors: Bartlewski P. M. , Beard A. P. , Chapman C. L. , Nelson M. L. , Palmer B. , Aravindakshan J. , Cook S. J. , Rawlings N. C.
Published: September 2002

The relationships between the development of antral follicles (growing from 3
to ≥5 mm diameter), hormone secretion (luteinizing hormone (LH),
follicle-stimlating hormone (FSH), oestradiol and progesterone), ovulation and
the formation of luteal structures in response to gonadotrophin-releasing
hormone (GnRH) were examined in 24 anoestrous Western White Face ewes
(May–July). Ewes were monitored by transrectal ovarian ultrasonography
for 34 days, commencing 15 days before the administration of GnRH. Following
treatment with GnRH, 83% (20/24) of ewes ovulated. Twenty-five per
cent of all ewes (6/24) subsequently had normal (full-life span) corpora
lutea (CL), 37% (9/24) had inadequate CL, 17% (4/24) had
both normal and inadequate CL, 17% (including three of four anovular
ewes and one ewe with inadequate CL) formed luteinized follicles and only
4% (1/24) did not ovulate or produce any luteal structure. None of
the variables of follicular growth (follicles reaching ≥5 mm diameter)
differed between follicles that either ovulated or failed to ovulate and there
was no evident correlation between the age or stage of development of
ovulatory sized antral follicles and the type of luteal structure formed,
except for luteinized unovulated follicles; these follicles all emerged within
3 days of GnRH injection. Mean serum concentrations of FSH and oestradiol
before treatment did not differ (P> 0.05) between
ewes with different ovarian responses, but peaks of fluctuations in serum
concentrations of FSH in daily samples were higher in ewes that produced
normal CL compared with ewes with inadequate CL. After GnRH treatment,
oestradiol secretion was higher in ewes that formed luteinized unovulated
follicles than in all ewes with inadequate CL (P>
0.05). The peak concentration of the GnRH-induced LH surge was higher and the
interval from GnRH to peak LH discharge was shorter in ewes with inadequate CL
compared with ewes that had normal CL after ovulation
(P> 0.05). In conclusion, ovulatory sized antral
follicles at a similar stage of their life span can give rise to either normal
or inadequate CL and a proportion of these follicles do not ovulate in
response to GnRH in seasonally anoestrous ewes. This suggests differences in
ovarian follicular responsiveness to gonadotrophic stimuli. Both the amplitude
of episodic elevations in daily serum FSH concentrations and the
characteristics of the pre-ovulatory LH surge may be important for
luteogenesis following ovulation.
Serum-soluble human leucocyte antigen class I and class II concentrations as an alternative diagnostic test for determining immune indices required for normal pregnancies
Authors: Vassiliadis Simon , Paflis Michael , Athanassakis Irene
Published: September 2002

The levels of maternal immunostimulation (required throughout the gestation
period) and immunosuppression (needed from the 8th week to labour), as
assessed by the mixed lymphocyte reaction (MLR), have been successfully
correlated with the outcome of pregnancy. Our laboratory has recently reported
that serum-soluble human leucocyte antigen (HLA) class I and II concentrations
can be predictive for successful pregnancy outcome. In fact, there is a direct
correlation between soluble class II concentrations and maternal
immunostimulation because, as expected, these serum HLA concentrations are
augmented in the first and second trimester of pregnancy and remain stable
thereafter. By the same token, serum HLA class I concentrations are low during
the first trimester, correlating with the required absence of
immunosuppression, whereas they increase in subsequent trimesters as
suppression becomes desirable for counteracting the maternal stimulation,
which may otherwise become dangerous to the fetus. In this study, we present
biological and statistical evidence that both states of maternal
immunostimulation and immunosuppression, reflected by serum soluble HLA class
II and class I antigens, do correlate with results obtained by standard MLR
and can be predictive of pregnancy failure. The establishment of statistically
significant correlations renders the measurement of soluble HLA a reliable
test for determining the immunological status of the gestating woman. The
unambiguous advantage of such an approach is that soluble HLA testing will no
longer require the 1 week delay necessary to obtain MLR results, a period
occasionally crucial for applying treatment to women whose immunological
indices call for immediate therapeutic intervention.
Nuclear transfer in human medicine and animal breeding
Authors: Trounson Alan
Published: September 2002

Cloning has a number of potential applications in human medicine and animal
breeding, but the efficiency of production of developmentally competent
embryos and healthy animal offspring needs to be improved. The primary
deficiency appears to be incomplete or abnormal nuclear reprogramming after
nuclear transfer, and it is hypothesized that epigenetic regulators of
transcription cannot always be converted to the embryonic pattern and this
leads to implantation failure, gestational abnormalities and poor health of
offspring. Research needs to be focused on this aspect of development for
nuclear transfer embryos. However, there is a gradual demand for commercial
application for cloning in animal production, transgenesis and animal
biopharmaceuticals, particularly in milk. These applications will expand in
the near future. There is little application of nuclear transfer in human
medicine at present, but important applications may be demonstrated for
prevention of the inheritance of mitochondrial mutations, prevention of
age-related aneuploidis in women, artificial gametes for sterile individuals
or couples and for therapeutic cloning to enable cell and gene therapies.
Identification and characterization of a gene coding a novel isoform of DEAD-box protein
Authors: Yin Lanlan , Li JianMin , Zhu Hu , Lin Min , Cheng Lijun , Wang Youqun , Zhou Zuomin , Sha Jiahao
Published: September 2002

A gene coding a novel isoform of DEAD-box protein named testicular DEAD-box protein (tDbp), presumably involved in testicular function, was identified and characterized. Testicular DEAD-box protein was cloned from a human testis cDNA library. The cDNA microarray hybridization showed that it was expressed at a higher level in adult testis than in embryo testis. Reverse transcription-polymerase chain reaction indicated that tDbp was specifically expressed in testis, but not in some other tissues.
Biotech prospects for the control of introduced mammals in Australia
Authors: Seamark Robert F.
Published: September 2002

More than twenty exotic vertebrate species are now listed as pests in
Australia. Collectively, these pests have a huge economic and environmental
impact and pose a major threat to Australia’s ecosystems and unique
biodiversity. Management of such pests on a continental scale is a major
challenge. Recent advances in biotechnology suggest alternatives to the lethal
diseases normally sought for use as biological control agents. One proposal,
being investigated in the Pest Animal Control Cooperative Research Centre,
Canberra, is the use of biotechnology to develop a new generation of agents
that act through controlling reproduction to prevent the build up of pest
populations. The core concept is fertility control through immunocontraceptive
vaccines delivered by viruses that specifically infect the target pest
population. Proof of this exciting concept has been obtained for the mouse
and, very recently, the rabbit, and a candidate vaccine vector identified for
the fox, portending better control of a trio of Australia’s most
pervasive pests. Other advances in biotechnology suggest ways to negate the
build up of both innate and acquired immune resistance in target pest
populations that normally act to limit the efficacy and effective life of
biocontrol agents in the field. Prospects for extending the use of virally
vectored vaccines to the field management of wildlife diseases are also
identified. Targets for such vaccines include a growing suite of emerging
diseases, hosted by Australia’s wildlife, which pose a threat to human
and livestock health. Numerous technical challenges remain to be addressed
before any of these new agents are ready for use in the field. However, the
major risk to their development is now no longer viewed as being technical,
but the failure to gain public acceptance for their use in the field. This
already significant risk is exasperated by the present heightened level of
public concern about all introductions of genetically modified organisms.
Bait-delivered cabergoline for the reproductive control of the red fox (Vulpes vulpes): estimating mammalian non-target risk in south-eastern Australia
Authors: Marks Clive A.
Published: September 2002

Cabergoline (CAB) is a potent dopamine agonist and an inhibitor of prolactin
(PRL). In red foxes (Vulpes vulpes), a single oral dose
of 100 g kg–1 CAB can cause abortions and
postnatal cub mortality from at least Day 21 of the 52-day pregnancy. The
abortifacient activity of CAB is owing to the suppression of PRL, which is
essential for luteotrophic support in some eutherian species. Postnatal cub
mortality probably results from a reduction in the development of the mammary
ductile system, which is also partially dependant on PRL during pregnancy.
This paper investigates the potential risks faced by non-target mammalian
species that may consume CAB baits intended for fox control. Baiting with CAB
is proposed from 1 August until 1 October each year, to correspond with the
time that most vixens are pregnant in south-eastern Australia. Thirty-four
endemic mammals in south-eastern Australia (9 eutherians and 25 marsupials)
are considered to be potentially bait-consuming (PBC) species. The percentage
overlap of pregnancy and birth periods for each PBC species was compared with
the duration of the proposed CAB baiting period. Only
Antechinus (3 species) and
Sminthopsis leucopushave greater than 40%
overlap, whereas overlap in endemic rodents ranges from 0% to
22%. Overall, most PBC rodent populations appear to face little risk
from CAB baiting, as their period of pregnancy does not overlap significantly
with the proposed CAB baiting period. The Antechinus
species, Phascogale tapoatafa and
Dasyurus maculatus are the only PBC mammals that are
seasonally mono-oestrous and are thus probably more susceptible to disruption
of breeding compared with polyoestrous species that may breed many times a
year. At a baiting density of 8 baits km–2,
theoretical bait availability for small dasyurids, rodents and peramelids is
low. This suggests a low potential for affecting these populations if CAB was
indiscriminate in affecting reproductive success in all mammal groups.
Presently, studies in a limited range of marsupials suggest that, unlike
eutherians, the marsupial corpus luteum is independent of pituitary control
and thus suppression of PRL is not likely to cause abortions in marsupials. As
yet, CAB has not been shown to be orally active in any PBC species other than
rodents and carnivores. Oral doses of CAB given post partum have not been
found to affect lactation in
Sminthopsis crassicaudata,Trichosurus vulpecula,
Macropus eugenii
andSetonix brachyurus. Further studies are required in
order to assess the potential for high doses of oral CAB to affect pre-partum
mammary development and early lactation post partum, especially in peramelids
and larger dasyurids. Highly target-specific baiting techniques, may eliminate
most PBC species from being exposed to CAB and these are briefly discussed.
Opinion: The future fertility of mankind: effects on world population growth and migration
Authors: Short R. V.
Published: September 2002

The world’s population, currently just over 6 billion, is projected to
increase to 9–10 billion by the year 2050. Most of this growth will
occur in the developing countries of Asia, where there is an enormous unmet
demand for contraception, while an increasing number of developed countries
will have declining populations. The human immunodeficiency virus (HIV)
pandemic will target developing countries, with India destined to become its
new epicenter. By 2050, there may be 1 billion HIV-infected people in the
world. The significant protective effect of male circumcision may spare
Islamic countries, such as Pakistan, Bangladesh, Iran and Indonesia, from the
worst effects of the pandemic. Australia will be increasingly threatened by
the high rates of population growth of her Asian neighbours. This, coupled
with political instability and sea-level rises as a consequence of global
warming, will turn the present trickle of refugees from a variety of Asian
countries seeking safe haven on our sparsely populated northern coastline into
a veritable flood. There will come a time when we have neither the manpower,
nor the means, nor even the moral right to intercept, detain or repatriate the
thousands who will come in peace, in search of a better life. However, if
Australia is to stabilize its future population at around 23 million, which
seems highly desirable on ecological grounds, then the net immigration rate
must be limited to approximately 50000 people per year. Because the final
point of departure for all these refugees is Indonesia, it is essential that
Australia maintains good relations with Indonesia, so that together we can
attempt to manage the refugee problem. However, Indonesia’s own
population is destined to increase by 100 million in the next 50 years, which
will only exacerbate the situation. Australia would be well advised to make a
major increase in its paltry financial assistance to Indonesia’s
excellent family planning programmes, which are currently starved of funds.
Helping Indonesia to contain its population growth is Australia’s best
long-term investment for its own future.