bluuebunny/crossref_metadata_2025 huggingface dataset:
Sustained growth and increased tolerance to glyphosate observed in a C3 perennial weed, quackgrass (Elytrigia repens), grown at elevated carbon dioxide
Authors: Ziska Lewis H. , Teasdale John R.
Published: September 2002

Although the response of crop plants to rising atmospheric carbon dioxide
concentration ([CO2]) has been well
characterized, little is known concerning the long-term growth and/or
photosynthetic response of peren-nial weeds. The growth and photosynthetic
characteristics of three cohorts of a perennial C3 weedy
species, quack-grass (Elytrigia repens (L.) Nevski) were
examined at ~380 µmol mol−1 (ambient)
and 720 µmol mol−1 (elevated)
[CO2] in temperature-controlled greenhouses
during 1998 and early 1999. Different cohorts were used to assess the
sensitivity of growth, photosynthesis and glyphosate tolerance to elevated
[CO2] for different stages in the life cycle
of quackgrass. For the ‘old’ cohort, planted on Day of Year (DOY)
187, elevated [CO2] resulted in a consistent
stim-ulation of single leaf photosynthesis, vegetative and whole plant biomass
relative to the ambient [CO2] condition over a
231-d period. Data from the ‘intermediate’ (DOY 268) and
‘young’ cohorts (DOY 350) indicated that the stimula-tion of
biomass at the elevated [CO2] was
time-dependent. To determine if the observed stimulation of growth at
ele-vated [CO2] altered tolerance to chemical
weed control, glyphosate
[(N-phosphonomethyl)glycine] was applied to
each cohort and each [CO2] treatment at rates
of 0 (control) and 2.24 kg ai ha−1 (sprayed).
Tolerance was determined by following the growth and slope of each cohort at
the growth [CO2] treatment for a 28-d period
following glyphosate application. For the young cohort,
[CO2] had no affect on glyphosate tolerance;
however, an application rate of 2.24 kg ai ha−1,
reduced but did not eliminate growth for the intermediate and old cohorts
grown at elevated [CO2]. The basis for
increased glyphosate tolerance at elevated
[CO2] for these cohorts was unclear, but was
not related to plant size at the time of glyphosate application. Data from
this experiment indicate that sustained stimula-tion of photosynthesis and
growth in perennial weeds could occur as atmospheric
[CO2] increases, with a reduction in chemical
control effectiveness and potential increases in weed/crop competition.
Nutrient uptake patterns over the surface of germinating wheat seeds
Authors: Shabala Sergey , Newman Ian , Wilson Stephen , Clark Robert
Published: September 2002

K+, Ca2+ and
H+ flux profiles were studied around the surface of
germinating wheat (Triticum aestivum L. cv. Machete)
seeds using a non-invasive microelectrode technique. The seed surface was
scanned every 500 µm along the longitudinal axis, and net ion fluxes
were measured 2 min and 1, 4 and 24 h after seed rehydration com-menced.
Functionally different seed zones exhibited different ion exchange patterns,
which also changed differently with time. One h after seed rehydration, the
peak of H+ extrusion was observed in the
embryo-scutellum region. By 24 h this peak had shifted towards the region of
radicle emergence, and its magnitude had increased 5-fold. By con-trast,
H+ activity in the endosperm region decreased
noticeably during this period. At the same time,
Ca2+ flux shifted from initial net influx to efflux
in the embryo and scutellum zones. Most striking were
K+ flux profiles, with large
K+ efflux observed at each end and almost zero flux
near the geometrical center of the seed. Significant
K+ extru-sion from the embryo end was observed for
as long as 24 h after seed rehydration and was not related to the loss of
membrane integrity. Seed treatment with metabolic inhibitors (vanadate and
tetraethylammonium) caused signifi-cant changes in both
H+ and K+ fluxes
suggesting that at least part of the measured fluxes originated from
activities of plasma membrane transporters. We discuss possible mechanisms
responsible for the observed regularities and question whether the seed coat
in wheat caryopses is as ion-impermeable as previously believed.
Source physiology and assimilate transport: the interaction of sucrose metabolism, starch storage and phloem export in source leaves and the effects on sugar status in phloem
Authors: Komor Ewald
Published: September 2002

Phloem loading of sucrose is decisive for the
speed of mass flow, because sucrose is the dominant solutein the sieve tube
sap of nearly all plant species. The export rate of carbon is linearly
correlated to the concentration of sucrose in green leaves. Saturation of
export was not observed, because surplus of assimilates is converted to
starch, a process which is regulated by the sucrose level in the cytosol.
Consequently, an increase of sucrose synthesis by overexpression of SPS did
not enhance carbon export (at least under normal ambient conditions).
Saturation of sucrose export could be observed only in experimental systems,
where sucrose was fed directly to the phloem (e.g. in
Ricinus seedling) or where constraints on transport
activity were imposed by genetic manipulation either on the transporters (e.g.
in sucrose transporter antisense plants) or on the path of sucrose (e.g. in
plants trans ormed with TMV movement protein, or by incubation in salts). The
balance between carbon storage and carbon export is subject to adaptation to
meet growth requirements under special circumstances. For example, in a
starch-deficient mutant, the day time export rate is nearly doubled compared
to wild type plants. Furthermore, plants under short day illumination greatly
accelerated starch storage compared to plants under long day illumination (a
modulation which persists even a few days after a shift to long day
conditions). Plants with a higher assimilation rate due to elevated ambient
CO2 increase the nightly carbon export rate, whereas the export rate in day
time rate appeared to work at its upper limit. The overall efficiency of
sucrose export and incorporation into biomass is ca
0.65, which is close to the theoretical value of 0.75. Sucrose transport along
the phloem strands is modulated according to the input at the source, but the
individual phloem strands show also partial coordination with respect to
sucrose concentrations (as revealed by NMR-imaging), especially obvious after
physical interruption of some vascular bundles.
Assimilate transport and partitioning in fungal biotrophic interactions
Authors: Hall John L. , Williams Lorraine E.
Published: September 2002

There are two major fungal biotrophic
interactions with higher plants: pathogenic biotrophs such as mildews and
rusts that cause substantial losses in crop yields, and mutualistic fungi that
form mycorrhizas and aid the uptake of phosphate and other minerals from the
soil with considerable agronomic benefits. Both are dependent on the plant for
the supply of carbon, yet much remains to be resolved concerning the transport
and partitioning of photoassimilates in these associations. In both
associations, specialised membranes interfaces are formed which are considered
to be the primary sites of nutrient transfer between plant and fungus. A range
of solutes may cross these interfaces, although glucose appears to have a
particularly important role. Molecular techniques are being used to identify
the specific membrane transporters involved at the interface. The
establishment of these biotrophic inter-actions also has a major effect on the
metabolism and transport activity of the host plant that affects its
source–sink balance. Increases in certain invertase activities and in
hexose transporters are especially marked. Again, the introduction of
molecular biology to these problems is beginning to provide the information on
the cellular locations and coordination of these host cell responses that is
required in order to understand how partitioning is regulated in these plant
fungal interactions.
Pathway and control of sucrose import into initiating cotton fibre cells
Authors: Ruan Yong-Ling , Llewellyn Danny J. , Furbank Robert T.
Published: September 2002

This paper originates from a presentation at the International Conference on Assimilate Transport and Partitioning, Newcastle, NSW, August 1999
Our aim is to unravel the mechanisms controlling fibre cell initiation from
the epidermis of cotton (Gossypium hirsutum L.) ovules.
We compared the development of fibres and trichomes in wild type cotton and a
fibreless seed (fls) mutant, and determined the cellular
pathway of sucrose transport into fibre initials on the day of anthesis.
Although fibre initiation is inhibited in the fls
mutant, leading to the fibreless phenotype, trichome development in other
parts of the plant is normal. Confocal imaging analysis revealed that the
fluorescent molecule, 5(6)-carboxyfluorescein, which is transported
symplastically, moved readily from the integument phloem into initiating
fibres. Plasmolysis studies showed that the fibre initials and adjacent
non-initiating ovule epidermal cells have similar osmotic potential.
Immunolocalisation analysis showed the absence of sucrose transporter proteins
in the initiating fibre, but their abundance in the transfer cell precursors
at the innermost integument. These results (i) demonstrate that fibre cell
initiation is controlled by unique mechanism(s) that differ from that for
normal trichome development; (ii) show a symplastic pathway of sucrose import
into initiating fibres and strengthen the current opinion that sucrose
synthase is likely to be the key enzyme mobilising sucrose into initiating
fibres; and (iii) suggest that the initial protrusion of the fibre cells above
the ovule surface is largely achieved by increased cell wall extensibility
rather than higher turgor as is commonly thought.
Altitude of origin influences stomatal conductance and therefore maximum assimilation rate in Southern Beech, Nothofagus cunninghamii
Authors: Hovenden Mark J. , Brodribb Tim
Published: September 2002

Gas exchange measurements were made on saplings of Southern Beech,
Nothofagus cunninghamii (Hook.) Oerst. collected from
three altitudes (350, 780 and 1100 m above sea level) and grown in a common
glasshouse trial. Plants were grown from cuttings taken 2 years earlier from a
number of plants at each altitude in Mt Field National Park, Tasmania.
Stomatal density increased with increasing altitude of origin, and stomatal
con-ductance and carbon assimilation rate were linearly related across all
samples. The altitude of origin influenced thestomatal conductance and
therefore carbon assimilation rate, with plants from 780 m having a greater
photosynthetic rate than those from 350 m. The intercellular concentration of
CO2 as a ratio of external CO2
concentration
(ci/ca)
was similar in all plants despite the large variation in maximum stomatal
conductance. Carboxylation efficiency was greater in plants from 780 m than in
plants from 350 m. Altitude of origin has a strong influence on the
photo-synthetic performance of N. cunninghamii plants
even when grown under controlled conditions, and this influence is expressed
in both leaf biochemistry (carboxylation efficiency) and leaf morphology
(stomatal density).
Temperature effects on symplasmic and apoplasmic phloem loading and loading-associated carbohydrate processing
Authors: Schrier Ard A. , Hoffmann-Thoma Gudrun , van Bel Aart J. E.
Published: September 2002

This paper originates from a presentation at the International Conference on Assimilate Transport and Partitioning, Newcastle, NSW, August 1999
Given the fact that plant species with a type 1 (symplasmic) minor vein
ultrastructure seem to dominate in the tropics and subtropics, and species
with a type 2 (apoplasmic) minor vein ultrastructure in the temperate and
boreal climate zones, a cold sensitivity of symplasmic phloem loading was
postulated. Electron microscopic observations were taken as support for this
proposal. The objective of the present work was to test this postulate by
measuring physiological parameters correlated to phloem loading. Carbohydrate
levels in the leaf, minor vein loading of
14CO2-derived assimilates in leaf
segments and exudation of sugars and 14C-labelled
compounds in several species from families with known phloem-loading pathways
were compared in 10 and 20˚C-adapted plants at both 10 and 20˚C. No
essential differences in response to temperature between symplasmically and
apoplasmically phloem-loading species were observed. Carbohydrate availability
for export was essentially similar, phloem loading was fully operative at
10˚C, and exudation of sugars equally reacted to low temperature in
symplasmic and apoplasmic species. Apparently, the geographical distribution
of type 1 and 2 species is not explained by a difference in temperature
sensitivity of the phloem-loading mode.
The conversion of carbon and nitrogen into starch and storage proteins in developing storage organs: an overview
Authors: Kavakli I. Halil , Slattery Casey J. , Ito Hiroyuki , Okita Thomas W.
Published: September 2002

In this article we provide an overview on
recent developments in starch and storage protein biosynthesis, two seemingly
distinct biochemical processes, which have been shown to be inter-dependent
based on results from genetic and transgenic studies. The pathway of carbon to
starch in cereal seeds has been found to be substantially different from other
plants in having ADPglucose, the precursor of starch biosynthesis, formed
mainly in the cyto-plasm in addition to the normal site of synthesis, the
plastid. Analysis of starch mutants and the use of antisense technology have
shed considerable light on the possible roles of individual starch synthase
and branching enzyme isoforms as well as those of enzyme activities normally
associated with a degradative function in starch formation. Analysis of
storage protein in the model system rice indicates that sites of protein
synthesis and compartmentation of macromolecules are stratified within
specific intracellular regions. The possible implications of this
intracellular partitioning of carbon (starch) and nitrogen (storage protein)
utilization are discussed.
Proteins in the sieve element-companion cell complexes: their detection, localization and possible functions
Authors: Hayashi Hiroaki , Fukuda Akari , Suzui Nobuo , Fujimaki Shu
Published: September 2002

Many kinds of proteins have been found in the
sieve element–companion cell complexes by the analyses of phloem sap and
microscopic observations. The cDNAs, which encode some of these sieve-tube
proteins, have already been cloned. As mature sieve elements lack nuclei and
most ribosomes, sieve-tube proteins have been hypothesized to be synthesized
in the companion cells and then transported to the lumina of the functional
sieve tubes through the plasmodesmata connecting the companion cells and sieve
elements. Soluble proteins present in the sieve tubes can be collected by
several techniques, such as incision or the aphid technique. The composition
of the proteins in the phloem sap is unique compared with that of tissue
extract, suggesting these proteins have important roles for the development
and functions of sieve tubes.
Comparison of the transport properties of three plant sucrose carriers expressed in Xenopus oocytes
Authors: Zhou Jing-Jiang , Miller Anthony J.
Published: September 2002

This paper originates from a presentation at the International Conference on Assimilate Transport and Partitioning, Newcastle, NSW, August 1999
Previous work has shown different patterns of expression for the three plant
sucrose transporters PmSUC1, PmSUC2 and AtSUC1. Each carrier may therefore
have different properties appropriate for the transport function at each
location in the plant. To test this hypothesis, a detailed characterisation of
each carrier was performed by expressing the protein in
Xenopus oocytes. All three carriers were functionally
active in oocytes and transported both sucrose and maltose with the sugars
eliciting inward currents, which increased at more negative membrane voltages.
This effect was greater for AtSUC1 and PmSUC1 than for PmSUC2. The affinities
of the carriers for each sugar were different, with PmSUC2 having a 10-fold
higher Km for sucrose compared to
AtSUC1 and PmSUC1. However, these values for all three carriers were dependent
on the external pH and membrane voltage. For both PmSUC1 and PmSUC2 the
maximal sugar transport was achieved at external pH values of 6.5–7.5,
values which do not appear to be consistent with a proton-coupled mechanism of
transport. However, the normal saline used for oocyte experiments contains
relatively high concentrations of NaCl that could interfere with the function
of the carrier protein. To test this idea the sucrose-elicited currents were
measured in saline containing lower concentrations of these ions. Sodium, but
not chloride, ions modified the sugar transport activities of the carriers and
these effects were different for each carrier, inhibiting AtSUC1 and PmSUC1,
but stimulating PmSUC2. The properties of each carrier are discussed in
relation to their expression in oocytes and what is known about their pattern
of expression in planta.
Effects of elevated CO2 concentration on photosynthetic acclimation and productivity of two potato cultivars grown in open-top chambers
Authors: Schapendonk Ad H.C.M. , van Oijen Marcel , Dijkstra Paul , Pot C. Sander , Jordi Wilco J.R.M. , Stoopen Geert M.
Published: September 2002

In two subsequent years, an early maturing potato cultivar with low leaf area
index (LAI) and a late cultivar with high LAI were grown at concentrations of
350 and 700 L CO2 L–1 in
open-top chambers. The average increase of tuber dry matter yield by elevated
CO2 was 27% in 1995 and 49% in 1996.
During the first weeks after planting, elevated CO2
stimulated the light-saturated rate of photosynthesis
(Amax) of both cultivars by
80%. However, Amax under
elevated CO2 declined to the level of the
low-CO2 treatment in the course of the growing season.
In 1995 this convergence due to acclimation of photosynthesis was completed
within 6 weeks, but in 1996, acclimation proceeded until the end of the
growing season. Photosynthetic acclimation was accompanied by a reduced
Rubisco content, and was correlated more closely with accumulation of sucrose
than of starch. From fluorescence measurements it was concluded that, in
contrast to the carboxylation efficiency, the efficiency of photosynthetic
reactions centers was not affected by acclimation to elevated
CO2. The faster photosynthetic acclimation in 1995
coincided with overall lower values of
Amax, crop growth rate and growth
response to elevated CO2. It is shown that the
indeterminate growth pattern of potato with its large sink capacity does not
preclude acclimation. The effect of acclimation on yield was quantified by
computer simulations. The simulated results indicated that photosynthetic
acclimation reduced the positive effect of elevated CO2
on tuber yield by 50%.
In vitro development of green fluorescent protein (GFP) transgenic bovine embryos after nuclear transfer using different cell cycles and passages of fetal fibroblasts
Authors: Roh Sangho , Shim Hosup , Hwang Woo-suk , Yoon Jong-taek
Published: September 2002

Nuclear transfer using transfected donor cells provides an efficient new
strategy for the production of transgenic farm animals. The present study
assessed in vitro development of nuclear transfer
embryos using green fluorescent protein (GFP) gene-transfected bovine fetal
fibroblasts. In experiment 1, bovine fetal fibroblasts (BFF) were transfected
with linearized pEGFP-N1 by electroporation, and the enucleated oocytes were
reconstructed by nuclear transfer of transfected cells (BFF-GFP). The rates of
blastocyst formation did not differ significantly between BFF and BFF-GFP
(18.2% v. 15.6%). In experiment 2, before
nuclear transfer, the donor cell stage was synchronized by serum deprivation
or forming a confluent monolayer. The rates of cleavage (67.1%
v. 71.8%) and blastocyst formation (15.8%
v. 15.5%) did not differ between confluent and
serum-starved cells after nuclear transfer. In experiment 3, the effects of
different passages of donor fibroblast cells on the development of nuclear
transfer embryos were investigated. Donor cells from ‘early’ (at
passage 8–16) showed better blastocyst development (18.9%) than
those from ‘late’ (at passage 17–32; 10.5%). In
conclusion, this study suggests that transgenic somatic cell nuclei from early
passages can be reprogrammed more effectively than those from late passages.
In addition, GFP, a non-invasive selection marker, can be used to select
transgenic nuclear transfer embryos.
Contribution of endogenous inhibin to the decline of the secondary surge of follicle-stimulating hormone in the rat
Authors: Arai Koji Y. , Watanabe Gen , Arai Katsuhiko , Uehara Kohkichi , Taya Kazuyoshi
Published: September 2002

The involvement of inhibin in the decline of the secondary surge of
follicle-stimulating hormone (FSH) was investigated in the rat. After
ovariectomy or treatment with inhibin antiserum conducted at 2300 hours during
pro-oestrus, plasma concentrations of FSH were maintained at high levels
compared with control rats. However, plasma FSH started to decline at 0500
hours during oestrus in both the groups. The same treatments conducted during
metoestrus markedly increased plasma FSH after 24 h (twofold compared with the
treatments during pro-oestrus), suggesting that the treatments sufficiently
depleted circulating inhibin. To examine whether the decline of plasma FSH
occurred through a transcriptional mechanism or through a translational
mechanism, FSH-β mRNA expression and the pituitary concentration of FSH
were measured. Neither ovariectomy nor inhibin immunization conducted during
the night of pro-oestrus, affected the pituitary concentration of FSH after 24
h, whereas a noticeable increase was observed after the treatments conducted
during metoestrus. In both stages, both ovariectomy and inhibin immunization
significantly increased FSH-β mRNA expression compared with control rats.
In contrast with the pituitary concentration of FSH, the effect of inhibin
immunization on FSH-β mRNA expression was not different between the
stages. The present data demonstrate the involvement of inhibin in the decline
of the secondary surge of FSH, and suggest that a factor or factors other than
inhibin may also be responsible for the fall in FSH. Changes in the pituitary
concentration of FSH and FSH-β mRNA expression suggest that
post-transcriptional mechanisms may be involved in the suppression of FSH
secretion during oestrus.
Baroreceptor and prostanoid control of fetal renal cortical blood flow and plasma renin activity
Authors: Lakhdir Farahaba R. , Tong Haiyan , Wood Charles E.
Published: September 2002

Renal function in the fetus is important for maintenance of fetal fluid and
electrolyte balance. This study was performed to test the role of
prostaglandins and their interaction with arterial baroreceptors and
chemoreceptors in the control of renal cortical blood flow during hypotension
produced by vena caval obstruction in late-gestation fetal sheep. We studied
18 time-dated, chronically catheterized, fetal sheep (124–136 days
gestation). Fetuses were either studied intact (n
= 11) or sinoaortic denervated (n
= 7), and each fetus was studied twice, with and without
pretreatment with indomethacin (0.2 mg kg –1 ,
i.v.). Each fetus was subjected to hypotension caused by vena caval
obstruction for 10 min. Before hypotension, renal cortical blood flow was
higher in the vehicle-treated sinoaortic denervated fetuses than in
vehicle-treated intact fetuses. The increased renal cortical blood flow
observed in the sinoaortic denervated fetuses was counteracted by
indomethacin, so that the difference between sinoaortic denervated and intact
fetuses was eliminated after indomethacin treatment. Hypotension decreased
renal blood flow equally in all groups. Plasma renin activity was increased in
response to hypotension in the intact fetuses, but not in the sinoaortic
denervated fetuses. Indomethacin treatment, by itself, did not alter plasma
renin activity. It is concluded that both arterial baroreceptors and
prostanoids influence renal blood flow. Further, renin secretion is influenced
by arterial baroreceptors and chemoreceptors and there is no apparent
modulatory effect of prostanoids on the baroreflex control of renin secretion.
Estrogens and falling sperm counts
Authors: Handelsman D. J.
Published: September 2002

Extravagant claims have been made repeatedly in recent years that human sperm
counts are falling and that global exposure to environmental estrogens are
responsible. The basis for these two distinct claims is reviewed. The claims
of falling human sperm output, reviving an old debate, are prompted by a paper
by Carlsen et al. (1992). This meta-analysis, however,
is marred by numerous flaws that invalidate its claims. Major defects include
severe heterogeneity of component studies, rendering them unsuitable for
aggregation, and defective data analysis based on arithmetic mean rather than
median, which showed no significant changes over time. This debate is likely
to remain unresolved until valid, representative population-based studies of
human sperm output can be achieved. None have been reported, or seem feasible
in the near future, and so alternative strategies, based on surrogate
variables for human male fertility not requiring sperm counts, need to be
developed and validated. The plausible hypothesis that prenatal estrogen
exposure might influence development of the human testis through effects on
Sertoli cell replication and sperm carrying capacity has, however, been
conclusively refuted by studies of boys born to women exposed to high doses of
oral diethylstilbestrol during pregnancy. Neither fertility nor sperm output
were adversely influenced by massive maternal estrogen exposure during
pregnancy, although minor urogenital malformations did occur. The still wider
claims of deteriorating male reproductive health, notably changes in
prevalence or incidence of hypospadias or cryptorchidism, also lack convincing
population-based evidence, although cancer registry data indicate a gradual
increase in testis cancer in some countries. In summary, the available
evidence does not support claims of falling sperm counts or any general
deterioration in male reproductive health. Population-based studies of valid
surrogate variables for male fertility not requiring semen analysis are
needed. If population-based evidence regarding male fertility or sperm output
could be generated, it is highly unlikely that prenatal estrogen exposure
could be a valid explanation of any deterioration as massive maternal exposure
to oral estrogen has negligible effects on male fertility or sperm output.
Toxicology of environmental estrogens
Authors: Safe Stephen H. , Pallaroni Lea , Yoon Kyungsil , Gaido Kevin , Ross Susan , Saville Brad , McDonnell Donald
Published: September 2002

It has been hypothesized that environmental contaminants that modulate
endocrine signaling pathways may be causally linked to adverse health effects
in humans. There has been particular concern regarding synthetic estrogens and
their role in disrupting normal development of the male reproductive tract.
Most estrogenic industrial compounds, such as bisphenol A (BPA) and
nonylphenol, typically bind estrogen receptors α (ERα) and
β (ERβ) and induce transactivation of estrogen-responsive
genes/reporter genes, but their potencies are usually ≥1000-fold
lower than observed for 17β-estradiol (E2). Selective estrogen
receptor modulators (SERMs) represent another class of synthetic estrogens
that are being developed for treatment of hormone-dependent problems. The
SERMs differentially activate wild-type ERα and variant forms
expressing activation function 1 (ER-AF1) and AF2 (ER-AF2) in human HepG2
hepatoma cells transfected with a pC3-luciferase construct, and these
in vitro differences reflect their
uniquein vivo biologies. The HepG2 cell assay has also
been used in our laboratories to investigate the estrogenic activities of the
following structurally diverse synthetic and phytoestrogens:
4′-hydroxytamoxifen; BPA;
2′,4′,6′-trichloro-4-biphenylol;
2′,3′,4′,5′-tetrachloro-4-biphenylol;
p-t-octylphenol;
p-nonylphenol; naringenin; kepone; resveratrol; and
2,2-bis(p-hydroxyphenyl)-1,1,1-trichloroethane (HPTE).
The results show that synthetic and phytoestrogens induce distinct patterns of
gene activation in HepG2 and U2 osteogenic sarcoma cells, suggesting that
these compounds will induce tissue-specific in vivo ER
agonist or antagonist activities. The predicted differences between these
compounds, based on results of the in vitrobioassay,
have been confirmed. For example, BPA inhibits E2-induced responses in the
rodent uterus, and HPTE and structurally related compounds are ERα
agonists and ERβ antagonists in assays carried out in HepG2 and other
cancer cell lines.
The role of estrogens in male skeletal development
Authors: Bilezikian John P.
Published: September 2002

The developing human skeleton is known to be influenced by the presence of sex
steroids. In girls, estrogens have been considered to be the dominant hormone,
whereas in boys, androgens have occupied a primary physiological role in terms
of bone mass accrual. Although these views are still current, recent
observations made of rare defects in estrogen receptor sensitivity or estrogen
synthesis have called attention to the importance of estrogens in the
developing male skeleton. In these human genetic models, the affected men have
demonstrated continuous linear skeletal growth, open epiphyses, lack of
pubertal growth spurt, and reduced bone mass. In the example of men with
aromatase deficiency, lacking estrogens from birth, administration of estrogen
led to impressive increases in bone density, maturation of the skeletal growth
plates, and cessation of linear growth. Animal models mimicking these human
syndromes by knockout technology, have tended to support these observations.
The data argue for a primary role of estrogens in the developing male
skeleton, while not diminishing the important role for androgens.
Comparison of the effects of in vitro and in situ storage on the viability of mouse ovarian tissue collected after death
Authors: Snow M. , Cleary M. , Cox S-L. , Shaw J. , Paris M. , Jenkin G.
Published: September 2002

Ovarian tissues, collected or salvaged from endangered species at the time of
gonadectomy or following their death, are being transported to genebanks for
storage with the assumption that they will (subsequently) yield sufficient
numbers of germ cells to help preserve the species. The present study aimed to
quantify the impact of delays in collecting and/or processing ovarian
tissue on the number of follicles in this tissue that remained normal after
grafting. The study compared the viability of ovarian tissue stored
in vitro (in phosphate-buffered saline) versus
in situ (in the body) either on ice or at room
temperature for 0 (non-stored fresh grafts), 3, 6, 12, 24 or 48 h. The
conditions of storage had significant effects on the total number of
morphologically normal follicles, with significantly more follicles in grafts
developing from in vitro-stored tissue than
in situ-stored tissue. Storage temperature and duration
of storage, but not the storage temperature alone, influenced follicle
survival. Tissue that was grafted immediately after collection (0 h) was best,
but normal follicles were recovered in grafts stored
in vitro (on ice or at room temperature) or
in situ (on ice only) for up to 48 h before grafting.
The rate of follicle loss over time was very rapid, with approximately
50% fewer follicles in grafts derived from tissue stored for only 3 h
compared with non-stored fresh grafts (0 h). The results show that viable
ovarian tissue can be salvaged from animals up to 48 h after death; however,
in order to best protect the follicle population, the ovaries should be
removed from the animal’s body as soon as possible.
Estrogenic effects on prostatic differentiation and carcinogenesis
Authors: Cunha Gerald R. , Wang Y. Z. , Hayward Simon W. , Risbridger Gail P.
Published: September 2002

Estrogens, alone or in combination with androgens, can induce aberrant growth
and/or malignancy of the prostate gland. Squamous metaplasia is an
abnormal form of prostatic epithelial differentiation elicited by exogenous
estrogen alone. Estrogens elicit their effects via estrogen receptors (ER) in
the prostate. Experiments using ERα and ERβ null mice
demonstrated that ERα, but not ERβ is essential in the
induction of prostatic squamous metaplasia. To determine the respective roles
of epithelial versus stromal ERα in this response, the following
tissue recombinants were constructed with prostatic epithelium (PRE) and
stroma (S) from wild-type (wt) and ERα knockout (αERKO)
mice: wt-S + wt-PRE, · αERKO-S +
αERKO-PRE, wt-S + αERKO-PRE and αERKO-S
+ wt-PRE. A metaplastic response to diethylstilbestrol (DES) was only
observed in wt-S + wt-PRE tissue recombinants. Tissue recombinants
containing αERKO-PRE and/or αERKO-S (ERKO-S
+ αERKO-PRE, wt-S + αERKO-PRE and
αERKO-S + wt-PRE) failed to respond to DES. Therefore, full
and uniform epithelial squamous metaplasia requires ERα in both the
epithelium and stroma. Estradiol (E2) in combination with testosterone (T) was
shown to be effective in inducing prostatic carcinogenesis in a tissue
recombinant model composed of rat urogenital sinus mesenchyme plus mouse
prostatic epithelium. A particularly efficient model of prostatic
carcinogenesis in mice involves T + E2 treatment of mice bearing
grafts of wild-type rat urogenital mesenchyme (rUGM) plus retinoblastoma gene
(Rb) knockout (Rb-KO) prostatic epithelium (rUGM
+ Rb-KO-PRE). Such rUGM + Rb-KO-PRE tissue recombinants
developed hyperplasia, atypical hyperplasia and invasive prostatic carcinoma
with high efficiency. During carcinogenesis in rUGM + Rb-KO-PRE tissue
recombinants, epithelial E-cadherin almost totally disappeared and epithelial
PCNA labeling was elevated. These epithelial changes were associated with
almost total loss of smooth muscle cells in the stroma. The results of this
study demonstrate that the absence of the Rb tumor
suppressor gene predisposes prostatic epithelial cells to hormonal
carcinogenesis.
Inhibitors of caspase homologues suppress an apoptotic phenotype in cultured rabbit corpora lutea
Authors: Abdo M. A. , Richards A. , Atiya N. , Singh B. , Parkinson S. , Hisheh S. , Dharmarajan A. M.
Published: September 2002

Apoptosis is a morphologically defined type of cell death initiated by various
stimuli that results in the activation of caspases (cysteine-containing
aspartate-specific proteases). In the present study, it was determined that
caspases are present during, and play a role in, corpus luteum (CL) apoptosis
in vitro. Pseudopregnancy was induced in rabbits with
100 IU human chorionic gonadotrophin. On Day 11 of pseudopregnancy, CL were
isolated and cultured for 0, 2, 4, 6, and 8 h in the absence of trophic
support to induce spontaneous apoptosis. Total RNA was extracted and analysed
for caspase-1 expression by Northern blot analysis. The results demonstrated
caspase-1 expression from 4 h. In the second part of the study, CL were
incubated without trophic support for 4 h with increasing concentrations of
three general caspase inhibitors, sodium aurothiomalate (SAM), iodoacetic acid
(IAA) and N-tosyl-L-phenylalanylchloromethylketone
(TPCK) , and two specific caspase inhibitors, N-acetyl (Ac)-Tyr-Val-Ala-Asp
(YVAD)-chloromethylketone (CMK) (Ac-YVAD-CMK) and Ac-Asp-Glu-Val-Asp
(DEVD)-aldehyde (CHO) (Ac-DEVD-CHO). At completion, DNA was isolated and
integrity assessed. Treatment of CL with SAM, IAA or Ac-DEVD-CHO effectively
suppressed apoptotic DNA fragmentation. The final component of the study was
to examine caspase-3 protein expression. Western blot analysis revealed a
significant increase in caspase-3 expression over the experimental
time-course. The results of the present study clearly demonstrate a
time-dependent link between the caspases, specifically caspase-3 and
spontaneous apoptosis in the rabbit CL.
Extra keyword: pseudopregnancy.
Lecithin-cholesterol acyltransferase activity during maturation of human preovulatory follicles with different concentrations of ascorbate, a-tocopherol and nitrotyrosine
Authors: Cigliano L. , Balestrieri M. , Spagnuolo M. S. , Dale B. , Abrescia P.
Published: September 2002

The enzyme lecithin–cholesterol acyltransferase (LCAT) transfers an acyl
chain from lecithin to cholesterol or oestradiol, thus playing a crucial role
in reverse cholesterol transport and follicular synthesis of potent long-lived
oestrogens. The mechanism of catalysis is biphasic, as it is based on a
phospholipase and an esterifying activity. Sulfhydryl groups were previously
reported to be required for the esterification step.
Lecithin–cholesterol acyltransferase has previously been shown to be
inhibited by thiol oxidants such as peroxynitrite. Peroxynitrite also converts
tyrosine to nitrotyrosines. In the present study, high levels of nitrotyrosine
associated with low LCAT activity, and vice versa, were found in human
preovulatory follicular fluids. Follicular fluids were also analysed for
oestradiol (E) and progesterone (P) concentrations. The E/P ratio, which
decreases as ovulation approaches, was used to evaluate the maturation status
of each follicle. Enzyme activity was negatively correlated with the E/P
ratio. Ascorbate (Asc) and α-tocopherol (Toc) were titrated in
follicular fluid and plasma to evaluate their accumulation or consumption in
the follicle. High LCAT activity was found in follicular fluids where Asc and
Toc had accumulated, whereas lower activity was associated with Asc and Toc
consumption. The consumption of both antioxidants was positively correlated
with the E/P ratio. The results suggest that as follicle maturation
progresses, Toc and Asc concentrations increase in follicular fluid, thus
protecting LCAT from oxidative damage and loss of activity.
Steroidogenesis, proliferation and apoptosis in bovine granulosa cells: role of tumour necrosis factor-α and its possible signalling mechanisms
Authors: Basini G. , Mainardi G. L. , Bussolati S. , Tamanini C.
Published: September 2002

This study was designed to investigate the presence of bioactive tumour necrosis factor-α (TNF-α) in bovine fluid collected from small (<5 mm) and large (>8 mm) follicles, as well as the production of the cytokine by the granulosa cells collected from the same type of follicles. Moreover, the effectiveness of 10, 1 and 0.1 ng mL-1 of human TNF-α (hTNF-α) in affecting the main parameters of granulosa cell function, progesterone (P4) and oestradiol-17β (E2) production, cell proliferation and apoptosis, was tested. In addition, the study aimed to determine whether the signalling mechanisms of TNF-α in these cells involve cAMP, nitric oxide or prostaglandin E2 (PGE2) and F2α (PGF2α). It emerged that bioactive TNF-α is present in follicular fluid from both types of follicles and can be measured in media conditioned by granulosa cells from large follicles. As for the effects of hTNF-α , it inhibits P4 production in cells from both types of follicles and stimulates E2 output in those from small follicles; it does not affect proliferation, but it stimulates granulosa cell apoptosis. Finally, the effects of hTNF-α on bovine granulosa cells are not mediated by nitric oxide or cAMP, as neither of these substances were affected by treatment with the cytokine; however, in some way, they could be mediated through PGE2 and PGF2α, the production of which was inhibited by TNF-α in cells from small follicles.
Levels of endothelin-1 in embryos from control and neonatal streptozotocin-induced diabetic rats, and their relationship with nitric oxide generation
Authors: Sinner Debora , Jawerbaum Alicia , Pustovrh Carolina , White Verónica , Capobianco Evangelina , Gonzalez Elida
Published: September 2002

Endothelin-1 (ET-1), a potent vasoconstrictor peptide and modulator of
vasoactive substances such as prostanoids and nitric oxide (NO), plays an
important role during embryo and fetal development. In this work, ET-1,
nitrate and nitrite, and prostaglandin E2
(PGE2) levels in embryos from control and neonatal
streptozotocin-induced (n-stz) diabetic rats were assessed, and the modulatory
pathways regulating the generation of these vasoactive agents investigated.
Endothelin-1 concentrations were found to be increased in embryos from n-stz
diabetic rats when compared with controls. Additions of spermine NONOate, a
nitric oxide donor, enhanced ET-1 levels in embryos from both control and
n-stz diabetic rats, whereas
NG-monomethyl-L-arginine,
a nitric oxide inhibitor, diminished embryonic ET-1 content. Thus, enhanced
ET-1 levels in the embryos from n-stz diabetic rats may be related to the
elevated NO levels found in those embryos. Additions of ET-1 or bosentan (an
endothelin A and endothelin B receptor antagonist), did not alter
PGE2 generation in embryos from either control or n-stz
diabetic rats. Endothelin-1 additions diminished nitrate and nitrite levels in
embryos from both control and n-stz diabetic rats, whereas bosentan stimulated
nitrate and nitrite generation in those embryos. In the present work, it was
found that ET-1 levels were enhanced in embryos from n-stz diabetic rats,
probably as a result of NO overproduction, an alteration which may be related
to embryonic abnormalities and growth delay. Endothelin-1 has been shown to be
a negative modulator of embryonic NO levels, a mechanism likely to be
important during development. Endothelin-1 may prevent damage induced by NO
overproduction in embryos from n-stz diabetic rats.
Lactational control of reproduction
Authors: McNeilly Alan S.
Published: September 2002

In most mammalian species lactation suppresses fertility. There is no doubt
that it is the suckling stimulus that provides the controlling signal, and, in
human reproduction, this is the only truly physiological signal that
suppresses fertility in normally nourished, healthy women. In breastfeeding
women, the return of normal fertility follows a relatively well-defined path
progressing through: an almost complete inhibition of gonadotrophin-releasing
hormone/luteinizing hormone (GnRH/LH) pulsatile secretion in the early
stages of lactation; return of erratic pulsatile secretion with some ovarian
follicle development associated with increases in inhibin B and oestradiol; a
resumption of apparently normal follicle growth associated with a normal
increase in oestradiol, but often an absence of ovulation, or formation of an
inadequate corpus luteum; and a return to normal ovulatory menstrual cycles. A
key element in controlling the rate of this progression is the impact of the
suckling stimulus on the GnRH pulse generator, a common feature of lactation
in those species for which there is information. The variability in the
duration of lactational amenorrhoea between women is related to the variation
in the strength of the suckling stimulus, a unique situation between each
mother and baby. Full breastfeeding can provide a reliable contraceptive
effect in the first 6 to 9 months, but the precise mechanisms whereby the
suckling stimulus affects GnRH pulsatile secretion remain unknown. Many
studies on the hypothalamic pathways that might be involved in the translation
of the neural suckling stimulus to suppression of hypothalamic GnRH secretion
have been undertaken, principally in rats. In women, suckling increases the
sensitivity of the hypothalamus to the negative feedback effect of oestradiol
on suppressing the GnRH/LH pulse generator, a mechanism that appears to be
common across species. In contrast, the role of prolactin in the control of
GnRH appears to be species-dependent, with the importance varying from none to
an important role in late or throughout lactation. In women, there is little
evidence for a role of leptin, opioids or dopamine, although this may merely
reflect the ethical dilemma of being able to give sufficient drug to test the
system in the mother since these drugs will pass through the breast milk to
the baby. Regardless of mechanism, practical guidelines for using
breastfeeding as a natural contraceptive have been developed, which allows
mothers to utilize the only natural suppressor of fertility in women as an
effective means of spacing births.
Assisted reproductive techniques for hybridization of camelids
Authors: Skidmore Julian A. , Billah M. , Short R. V. , Allen W. R.
Published: September 2002

The camelid family comprises the Old World camelids (or dromedary and Bactrian
camels) and the New World camelids (namely the llamas, alpacas, guanacos and
vicunas). Although the species within each group can hybridize among
themselves to produce fertile offspring, it is only recently that a hybrid
between New and Old World camelids has been reported. To create this hybrid,
semen was collected from male camels by artificial vagina (AV) and inseminated
into female guanacos (n= 9) and llamas
(n= 3) at the appropriate stage of their
follicular wave cycle. Similarly, guanaco and llama semen was collected, also
by AV, and inseminated into female camels (n=
42). Although several conceptions occurred, only one hybrid (camel
sire×guanaco dam) continued to term and was born alive after 328 days of
gestation, and another is pregnant at the time of writing (camel
sire×llama dam). Further studies are presently being carried out using
extraspecific embryo transfer to try and improve the success rate of live
offspring being born. Female guanacos (n= 4) are
treated with hormones to stimulate their ovaries to produce several follicles
before being inseminated with camel semen. Of the 12 camel recipients that
have to date received hybrid embryos (camel sire×guanaco dam), 10
conceived, but 9 of these subsequently aborted between 30 and 365 days and
only one recipient was still pregnant at the time of writing.
The promise and performance of progestogens as contraceptives
Authors: Fraser Ian S.
Published: September 2002

Progestogens were first suggested as possible contraceptives in the 1920s, but
it was not until the early 1960s that effective progestogen-only contraceptive
methods were developed. Since then it has become possible to deliver a range
of different progestogens at varying doses, by a variety of routes, over
greatly differing durations of time. Some of these systems have demonstrated
extraordinarily high contraceptive efficacy with relatively few side-effects
apart from unpredictable, but almost universal, disturbances of the menstrual
pattern. It is now recognized that some systems may exhibit substantial
non-contraceptive health benefits, which should become an important part of
the overall performance profile of each method. The high technology and
differing attributes associated with some of the systems raise important
considerations in relation to user’s perceptions and programmatic
requirements. Overall, progestogens are able to offer women a varied range of
valuable choices for contraception. The differing performance characteristics
of these methods now provide women with a major portion of their current
contraceptive choices.