bluuebunny/crossref_metadata_2025 huggingface dataset:
The Role of Sodium in the Conversion of Pyruvate to Phosphoenolpyruvate in Mesophyll Chloroplasts of C4 Plants
Authors: Brownell PF , Bielig LM
Published: January 2006

PEP formation from pyruvate was determined in mesophyll chloroplasts mechanically isolated from sodium-deficient and sodium-replete plants of the NADP malic enzyme-type C4 species, Kochia trichophylla. An extremely sensitive method for estimating PEP was developed which permitted determination of picomole quantities of PEP in small samples taken sequentially from the mesophyll chloroplast suspension concurrently with observations on oxygen evolution. It was shown that PEP formation requires light and depends upon the intactness of the chloroplasts. The rate of formation of PEP from pyruvate increased in the presence of the Hill reagent, oxaloacetate, thus indicating its dependence on non-cyclic photophosphorylation for the supply of ATP required in the conversion of pyruvate to PEP. The optimum inorganic phosphate concentration for PEP formation was approximately 16 mM. The rates of oxygen evolution and PEP formation were equivalent at concentrations of pyruvate up to 20 mM, suggesting tight coupling between electron transport and phosphorylation. In both Kochia trichophylla and the NAD malic enzyme-type, Panicum miliaceum, the rates of PEP formation were greater in the mesophyll chloroplasts from sodium-replete than from sodium-deficient plants. Chloroplasts resuspended in 'sodium-free'media containing less than 30 μM (0.7 ppm) sodium showed reduced rates of PEP formation compared with chloroplasts resuspended in media to which 1.0 mM (23 ppm) sodium had been added. Both media contained 10 mM 'sodium-free' KCI. These results indicate that sodium ions may be required to maintain the functional integrity of the mesophyll chloroplasts and that irreversible damage is sustained when sodium is absent during their isolation.
Reassessment of the Role of Calcium in Development of Bitter Pit in Apple
Authors: Saure MC
Published: January 2006

From an extensive evaluation of the literature on effects of orchard factors on bitter pit development, the following hypothesis has been derived. The primary factor causing bitter pit is high gibberellin (GA) levels late in the season, likely resulting from excessive root activity. The increased GA levels may cause increased permeability of cell membranes in the fruit close to vascular bundles, thereby resulting in increased sensitivity of the fruit cells to post-harvest water stress. Water stress, especially after harvest, may trigger the mechanism of bitter pit development if the primary factor, establishing susceptibility, prevails over factors that reduce susceptibility. Calcium (Ca2+) deficiency could be a secondary factor, increasing an existing risk of bitter pit development. Ca2+ may stabilise the cell membranes and reduce their permeability. However, high GA levels may hamper its movement to the fruit. Externally applied growth retardants, or ripening-related endogenous GA antagonists in the fruit flesh (e.g. ethylene and ABA), could aIso reduce susceptibility to bitter pit, independently of Ca2+, by antagonising the GA effect. The limitations of the present systems, which use Ca2+ content of the apple fruit to predict bitter pit, may reflect the secondary function of Ca2+ in bitter pit development.
Agrobacterium-Mediated Transformation and Expression of Foreign Genes in Medicago truncatula
Authors: Wang Jinghong , Rose RJ , Donaldson BI
Published: January 2006

Medicago truncatula Gaertn. (barrel medic) is a pasture legume and a model plant for studying the molecular genetics of the Rhizobium-legume symbiosis. Using the highly regenerable seed line Jemalong 2HA and Agrobacterium tumefaciens (LBA4404), Medicago truncatula can be reliably transformed. The binary vector utilised was pBI121 containing the nptII and uidA genes under the control of the NOS and CaMV 35S promoters, respectively. Kanamycin-resistant embryogenic calli were produced from 17% of the initial leaf explants and on average each one of these embryogenic calli produced a single regenerated plantlet. Regenerated plants showed varying gene copy number and gene location. GUS activity was detected in roots, stems and leaves. The progeny of a regenerated plant containing a single gene copy segregated in a Mendelian fashion. This study confirms the value of Jemalong 2HA for producing transgenic plants for biological and agricultural studies.
Single-Leaf Plantlet Bioassays for the Study of Root Morphogenesis and Rhizobium-Legume Nodulation
Authors: Rolfe BG , Mciver J
Published: January 2006

New plant bioassays have been developed to (a) study root morphogenesis in small seeded legumes, and (b) enable the routine examination of large numbers of independently transformed plants. In addition, these bioassays enable analysis of specific plant gene expression. The single leaf plantlet assay uses simplified plants that are without shoot meristems, have a photosynthetic organ, grow roots which can be nodulated by Rhizobium bacteria, and can form lateral roots. The rooted cotyledon assay (RCA) was developed to investigate root morphogenesis of clover plants. Studies showed that early in the development of the root there was a cotyledon-derived inhibitor that could inhibit the continued growth of Rhizobium-induced nodule primordia. However, the activity of this inhibitor diminished with continued growth and maturation of the root. Rhizobia that can synthesise wild-type Nod factors can partially overcome this inhibition of nodule formation, the Nod signals acting as 'anti-cotyledon inhibitors'. Comparison of the RCA plantlets with normal seedlings suggests that the rooted cotyledons have a slightly slower root maturation, which enables the experimentalist time to probe mechanisms underlying root development. The rooted leaf assay was developed so that the symbiotic and physiological properties of large numbers of transgenic plants could be studied. This is a rapid technique that can use either untransformed or recently transformed plant material, and avoids the potential problem of a disturbed hormone balance that is inherent in the use of 'hairy roots' generated by the use of the Agrobacterium rhizogenes-mediated transformation of small-seeded legumes.
Salt Enhances Photosystem I Content and Cyclic Electron Flow via NAD(P)H Dehydrogenase in the Halotolerant Cyanobacterium Aphanothece halophytica
Authors: Hibino T , Lee BH , Rai AK , Ishikawa H , Kojima H , Tawada M , Shimoyama H , Takabe T
Published: January 2006

To uncover the adaptation mechanisms of photosystems for halotolerance, changes in stoichiometry and activity of photosystems in response to changes of salinities were examined in a halotolerant cyanobacterium, Aphanothece halophytica. Photosynthetic O2 evolution was high even at high salinities. O2 evolution activity increased with increasing external concentration of NaCl, reached a maximum at 1.5 M NaCl, and then decreased. Similar salt dependence was observed for photosystem II activity. On the other hand, photosystem I activity increased concomitantly with increase in salinity. Photoacoustic measurements indicated that appreciable energy storage by photosystem I mediated cyclic electron flow at high salinities. Significant electron donation to photosystem I reaction centres through NAD(P)H-dehydrogenase complexes was observed in high salt media. The contents of cytochrome b6/f and photosystem II were almost constant under various salinity conditions, whereas the levels of chlorophyll α, photosystem I, soluble cytochrome c-553, and NAD(P)H-dehydrogenase increased in the cells grown with high salinities. These results indicate that salt specifically induces an increase of protein levels involving cyclic electron flow around photosystem I that may entail an important role for adaptation of Aphanothece halophytica cells to high salinities.
Vegetation Effects on the Isotopic Composition of Atmospheric CO2 at Local and Regional Scales: Theoretical Aspects and a Comparison Between Rain Forest in Amazonia and a Boreal Forest in Siberia
Authors: Lloyd J , Kruijt B , Hollinger DY , Grace J , Francey RJ , Wong SC , Kelliher FM , Miranda AC , Farquhar GD , Gash JHC , Vygodskaya NN , Wright IR , Miranda HS , Schulze ED
Published: January 2006

In order to understand the factors influencing the isotopic composition of air above and within plant canopies, equations quantifying the effects of photosynthesis, respiration and turbulent transport on the isotopic composition of the surrounding CO2 are developed. These equations are then extended to the regional scale, allowing the average isotopic composition of CO2 within the convective boundary layer to be related to the isotopic composition of tropospheric CO2, and to isotopic fractionations during ecosystem carbon exchange. Equations presented have the potential to be inverted, allowing direct estimation of isotopic fractionations by vegetation at the local and regional scales. Equations allowing the estimation of the extent of refixation of respired CO2 ('recycling') at the regional scale are also presented.
Using measurements of CO2 carbon isotopic composition in conjunction with ecosystem flux measurements, the theory is applied to a tropical rain forest in Amazonia and a boreal forest in Siberia. When examined on a ground area basis and over the course of a day it is observed that, by virtue of greater fluxes but similar isotopic fractionations, the tropical rainforest exerts much more influence over the isotopic composition of the surrounding air than does the boreal forest. Due to higher rates of ecosystem respiration, recycling of respired CO2 is modelled to be much greater for tropical rainforest, but values presented here are considerably lower than previously published estimates, the latter being based solely on the relationship between the isotopic composition and concentrations of CO2 within forest canopies. The reasons for these differences are examined.
Analysis of Inhibition of Photosynthesis Under Water Stress in the C4 Species Amaranthus cruentus and Zea mays: Electron Transport, CO2 Fixation and Carboxylation Capacity
Authors: Lal A , Edwards GE
Published: January 2006

Two C4 species, Amaranthus cruentus and Zea mays, were studied to evaluate the mechanism of inhibition of photosynthesis due to water stress. The net rate of carbon dioxide fixation (A) and transpiration (E) were measured by gas exchange, and stomatal conductance (gs) and intercellular CO2 (Ci) calculated, while the true rate of oxygen evolution (JO2) was calculated from chlorophyll fluorescence analysis. Following the withholding of water there was a progressive decrease in gs and E during the stress cycle. The results clearly indicate that, initially, Ci decreased with little effect on A (indicating the CO2 pump is providing sufficient CO2 for carbon assimilation), and that the eventual inhibition of photosynthesis by water stress was caused by a limited supply of CO2 to Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase). As A decreased during water stress, the photosystem II activity per CO2 fixed increased, a phenomenon also observed when well watered plants were provided with very low atmospheric levels of CO2, which is indicative of a decreased supply of CO2 to Rubisco. At the same time the RuBP pool/RuBP binding site on Rubisco increased, and the ratio of initial extractable activity of Rubisco to A increased, which suggests that neither RuBP regeneration nor Rubisco capacity is limiting photosynthesis. When plants were rewatered after photosynthesis had dropped to 5-10% of the original rate, both species showed near full recovery in 2-4 days.
Genotypic Variation in Light and Temperature Response of Photosynthesis in Nothofagus solandri Var. cliffortioides and N. menziesii
Authors: Sun OJ , Sweet GB
Published: January 2006

Responses of photosynthesis to light and temperature were studied in two Nothofagus species native to New Zealand: N. solandri var. cliffortioides (Hook. f.) Poole and N. menziesii (Hook. f.) Oerst.. Measurements of leaf photosynthesis were made in a controlled environment growth chamber at photosynthetic photon flux density between 0 and 700 μmol m-2 s-1 with temperatures set for 10, 20 and 25�C, on seedlings previously grown in a glasshouse from seed of three different origins. In both species, pronounced intraspecific variation was shown in dark respiration, light compensation point and light-saturated net photosynthesis (Amax). Seedlings of N. solandri showed higher dark respiration and light compensation levels than N. menziesii seedlings, but the two species did not differ in Amax. Change in temperature resulted in significant change in the response of photosynthesis to light in both N. solandri and N. menziesii. The differences between N. solandri and N. menziesii in light response of photosynthesis are discussed in terms of ecosystem dynamics of Nothofagus forests in New Zealand.
Effects of High Temperature on Membrane Stability and Chlorophyll Fluorescence in Glycinebetaine-Deficient and Glycinebetaine-Containing Maize Lines
Authors: Yang Genping , Rhodes D , Joly RJ
Published: January 2006

Pairs of homozygous near-isogenic glycinebetaine-containing (Betl/Bet1) and -deficient (betl/bet1) Fδ lines of Zea maysM L. (maize) were tested for differences in their responses to high temperature. Membrane integrity was evaluated by electrolyte leakage, and the in vivo photochemical activity of PSII was inferred from modulated chlorophyll fluorescence. Both variables were more markedly impaired by thermal stress in glycinebetaine-deficient lines. When whole plants, excised whole leaves or leaf segments were subjected to temperatures above 45�C, Betl/Bet1 lines exhibited less membrane injury than their near-isogenic betl/bet1 sister lines. An average difference of 2�C was observed between Betl/Betl and betl/betl lines in the critical temperature threshold which triggered catastrophic membrane damage in vitro. Betl/Bet1 lines also exhibited greater thermostability of PSII function. The empirical fluorescence parameters Fv/Fm and ΔF/F′m, indices of PSII quantum yield (ΦII) in the dark-adapted and illuminated states, respectively, were each markedly reduced in heat-treated leaves of betl/bet1 lines, relative to their Betl/Bet1 sister lines. These results strongly suggest that a single gene confering glycinebetaine accumulation (and/or a tightly linked locus) confers protection against heat destabilisation of leaf plasma membranes as well as the photochemical reactions of PSII in vivo.
Alleviation of Thermoinhibition in Chickpea Seeds by Putrescine Involves the Ethylene Pathway
Authors: Gallardo M , Sanchez-Calle I , Rueda PMD , Matilla AJ
Published: January 2006

Germination of chickpea (Cicer arietinum L.) was inhibited by supraoptimal temperatures of 30 or 35�C, but the inhibition was alleviated by a relatively low concentration (1 mM) of putrescine (Put). This allevation may be due to (a) stimulation of the 1-aminocyclopropane-1-carboxylate (ACC) synthase and ACC oxidase activities; (b) increased levels of ACC and decreased levels of 1-(malonylamino)cyclopropane-1-carboxylic acid (MACC); or (c) strongly increased ethylene production. Put at 10 mM did not alleviate thermoinhibition, although, as with Put at 1 mM, it did inhibit adenosyl-methionine (AdoMet) decarboxylase. Alleviation conditions resulted in: (a) an induced accumulation of free Put (S) and Put conjugated to substances of low (HS) and high (HP) molecular weight; (b) a decrease in spermidine (Spd) and spermine (Spm) (S and HP); and (c) no alteration in the levels of Spd and Spm (HS) with respect to the absence of Put (1 mM) at 30�C. In the presence of Put (10 mM), increased accumulation of Put (S, HS and HP) was detected, but with a sharp decrease of Spd and Spm (S and HS).
Constant and Interchanged Photoperiod Effects on the Rate of Development in Barley (Hordeum vulgare)
Authors: Kernich GC , Halloran GM , Flood RG
Published: January 2006

Indirect and direct influences of changes in photoperiod on the rate of development in barley (Hordeum vulgare L.) were examined using three Australian cultivars, Clipper, Galleon and Finlay. Each possessed little or no vernalisation response, and were grown at a constant temperature of 18�C with two treatments, one of each of two constant photoperiod regimes (10 and 18 h) while other treatments involved reciprocal transfer between them at either or both the double ridge (DR) and awn primordium (AP) stages of development. Under constant 18 h photoperiod, the lengths of all three development phases were shorter compared to the constant 10 h regime for Galleon and Clipper, while Finlay was relatively insensitive. The final number of leaves on the main culm was reduced by the constant 18 h photoperiod in Clipper and Galleon but Finlay was unaffected. The rate of development from DR to AP under 10 h photoperiod was increased by exposure to 18 h photoperiod from sowing (S) to DR, compared with plants exposed to 10 h photoperiod from S to DR. A similar response was noted for plants transferred at the AP stage, indicating that rate of development was determined both by its influence on prior as well as current photoperiod conditions. This 'memorised' response appears to be interactive, rather than additive, with the response of the plant to the current photoperiod. Direct and indirect effects of photoperiod on leaf and spikelet number, acting through their influences on the duration from S to DR and from DR to AP, were also discussed.
Optical Properties of Hairs During the Early Stages of Leaf Development in Platanus orientalis
Authors: Ntefidou M , Manetas Y
Published: January 2006

Young, developing leaves of plane (Platanus orientalis L.) possess a dense hair cover on both surfaces but, as the leaf matures, the hairs of the upper surface abscise, leading to a glabrous epidermis. Leaf hairs strongly attenuate visible radiation, partly due to high reflectance of the trichome layer and partly to the presence of an absorbing pigment, tentatively identified as the anthocyanidin peonidin, which was present in the hairs of exposed young leaves but was absent on leaves harvested from the interior of the canopy. It is suggested that leaf hairs, apart from other functions, may protect developing leaves against the photoinhibitory effect of excess light.
The Influence of Recovery Treatment on the Effects of a Brief Heat Shock on Wheat. II. Fractional Protein Accumulation During Grain Growth
Authors: Stone PJ , Nicolas ME , Wardlaw IF
Published: January 2006

In this study, we have sought to identify the nature of the response to both moderately high (25-32�C) and very high (>32�C) temperatures by examining their interactive effects on the accumulation of functionally important proteins during grain-filling. In particular, we wished to determine if the deleterious effects of very high temperature could be alleviated by subsequently cool conditions. To this end, wheat cv. Oxley was exposed to either 21/16 or 40/16�C (day/night) from 15 to 19 days after anthesis and subsequently grown under one of three temperature regimes until maturity: 21/16 (control), 27/22 or 30/25�C. Grain samples were taken throughout grain growth and analysed for protein content and composition. Wheat proteins were separated and quantified as albumin,globulin, monomer, SDS-soluble polymer and SDS-insoluble polymer using size-exclusion high-performance liquid chromatography.
The various protein fractions responded differentially and usually additively to moderately high and very high temperatures during grain-filling. Cool post-shock conditions did not alleviate the effects of very high temperature on grain protein composition. Heat treatments reduced polymer:monomer ratio because the accumulation of monomer was reduced less than that of polymer.
The Developmental Stage During Which Boron Limitation Causes Sterility in Wheat Genotypes and the Recovery of Fertility
Authors: Rawson HM
Published: January 2006

Sterility in wheat in parts of the subtropics has been linked primarily with low-boron soils and its variability between years and locations with variation in the weather. This paper shows, from reciprocal transfers of plants between adequate and zero boron root media at different developmental stages, that the period during which florets are sterilised by boron insufficiency can be very short. For any ear it extends from after its flag leaf tip has emerged until shortly after the flag leaf has become fully expanded. This critical period of up to 1 week in length has already passed when the ear begins to emerge. Because tillers are sequential, the critical stage for the whole plant is longer than 1 week. It was shown that ears could also be sterilised by enclosing the whole plant in a clear plastic bag during this critical period, even though the plants were growing with adequate boron provided in sub-irrigated gravel culture. It is suggested that one of the effects of enclosure is to prevent transpiration and possibly the associated uptake and movement of boron to the reproductive growth centres. The six genotypes tested did not differ in the developmental stage at which they were sensitive, and all were completely sterile when they were grown without boron up to and including that stage. However, it appeared that a prior period in adequate boron had a different effect on sterility amongst genotypes. One genotype (Fang 60) showed evidence of a boron reserve that could be utilised even after a period equivalent to 3 phyllochrons whereas others appeared to have no boron pool. Ears which were fully sterilised by inadequate boron could have their fertility raised marginally by a spray of boric acid even several days after they had emerged. The implications of these results to grain yield in the subtropics are discussed.
An Anionic, Stem-Specific Flax Peroxidase cDNA With C-Terminal Motifs Also Found in a Blue Copper-Type Pea Protein Correlated With Lignin Deposition
Authors: Omann F , Tyson H
Published: January 2006

A flax (Linum usitatissimum L.) peroxidase cDNA (FLXPER1) was isolated from a �gt10 library made from RNA derived from shoot tissue of the cultivar Stormont Cirrus, by screening with probes encoding amino termini of flax peroxidases. The probes were obtained by PCR amplification of the library with the �gt10 reverse primer 5'CTTATGAGTATTTCTTCCAGGGTA3' flanking the Eco RI cloning site, and a mixed oligonucleotide derived from the catalytic domain (HFHDCFV) found in all plant peroxidases. FLXPER1 is the second flax peroxidase to be so isolated and described, following the previously documented FLXPER2 (Omann et al. 1994, Genome 37, 137-147). These two cDNAs are the completely sequenced members of a family currently encompassing FLXPER1 to FLXPER4, all isolated from the same �gt10 library. FLXPER3 and 4 will be separately described and related to FLXPER1, 2.
The FLXPER1 deduced amino acid sequence reveals a signal peptide of 27 amino acids, and an anionic mature protein with seven potential N-linked glycosylation sites in its 332 amino acids (38.25 kDa; pI 4.38). The FLXPER1 C terminus is similar to plant peroxidases with a putative C-terminal vacuolar targeting signal, but also contains amino acid motifs with striking homologies to the membrane anchoring motifs of a pea blue copper type protein correlated with lignin deposition. Northern blot analysis demonstrated its stem specific expression. Southern blots suggested one to five copies of FLXPER1 in the flax genome, compared with one to two for FLXPER2. FLXPER1 resembles cucumber, poplar and tobacco amino acid sequences; its asymmetry in codon usage coincides with that of other dicotyledon peroxidases, i.e. much lower than in monocotyledon peroxidases.
Arachidonic acid-induced acrosomal loss in the spermatozoa of a marsupial, the tammar wallaby (Macropus eugenii)
Authors: Sistina Yulia , Rodger John C.
Published: January 2006

Tammar wallaby spermatozoa were induced to undergo acrosomal loss when
incubated with arachidonic acid (AA). Ultrastructural examination indicated
that the AA-induced acrosomal loss occurred via multiple point fusions between
the outer acrosomal membrane and the overlying plasma membrane. This form of
acrosomal loss mimicked the physiological acrosome reaction (AR) seen in the
sperm of eutherian mammals. The fusion event was limited to the acrosomal
region of the plasma membrane and did not proceed past the peri-acrosomal
ring. The entire acrosome was lost after AA treatment leaving no evidence of a
persistent equatorial segment-like region. Ultrastructural evidence of AR-like
membrane fusion was seen immediately on addition of 50 µg
mL-1 AA and a large proportion of sperm examined after
five min incubation were in the late stages of membrane fusion. Longer-term
incubation with AA had deleterious effects on wallaby sperm motility. It
remains to be determined whether the AA-induced membrane fusion observed here
indicates that AA is involved in the marsupial AR. However, pretreatment of
sperm with the protein kinase C (PKC) inhibitor HMG significantly reduced
AA-induced acrosomal loss suggesting that AA may have acted via PKC. If this
is so, AA is probably physiologically significant and a novel pathway may be
operating during AR induction in marsupials.
Asynchronous meiotic progression in porcine oocytes matured in vitro: a cause of polyspermic fertilization?
Authors: Grupen Christopher G. , Nagashima Hiroshi , Nottle Mark B.
Published: January 2006

The progression of meiosis in porcine oocytes
maturedin vitro was examined and the effect of
maturation interval on the incidence of polyspermic fertilization and
embryonic development in vitro was investigated. In
Experiment 1, it was found that oocytes selected for
in vitro maturation varied considerably in terms of
their meiotic progression. Approximately half of the oocytes were already
undergoing germinal vesicle breakdown at the start of maturation while the
remainder were at the intact germinal vesicle stage. These two populations of
oocytes developed to the metaphase-II stage by 24 h and 36 h of maturation
respectively. Maturation for 40 h and 44 h did not increase the percentage of
oocytes at metaphase-II stage observed at 36 h. In Experiment 2, reducing the
maturation interval from 44 h to 36 h did not affect the percentage of oocytes
penetrated but did decrease the rate of polyspermic fertilization (5%
v. 34%; P < 0
·05). In Experiment 3, development of the embryos produced
in vitro was assessed after culture for seven days.
Reducing the maturation interval from 44 h to 36 h decreased the percentage of
embryos developing to the 8-cell (9% v.
18%; P < 0 · 05), morula (3%
v. 10%; P < 0 ·
01), and blastocyst (1% v. 8%;
P < 0· 001) stages. These results suggest that
maturation for 44 h gives rise to a population of ‘aged’ oocytes
which is susceptible to polyspermic fertilization.
Immunohistochemical localization of placental leucine aminopeptidase/oxytocinase in normal human placental, fetal and adult tissues
Authors: Nagasaka T. , Nomura S. , Okamura M. , Tsujimoto M. , Nakazato H. , Oiso Y. , Nakashima N. , Mizutani S.
Published: January 2006

While oxytocinase is known to exist in pregnancy serum and placenta, the
present study describes the expression of the mRNA for this enzyme in a wide
variety of other human tissues. Northern blot analysis was used to detect the
mRNA, with a probe derived from a cDNA for oxytocinase/placental leucine
aminopeptidase (P-LAP). Both the distribution and localization of
immunoreactive oxytocinase/P-LAP protein have been determined
immunohistochemically by use of an anti-P-LAP antibody in normal placental,
fetal and adult tissues. In placental tissues, only syncytiotrophoblasts were
stained positively. In both fetal and adult tissues, positive staining was
obtained in vascular endothelial cells, gastrointestinal mucosal cells,
epithelial cells of hepato-biliary, pancreato-biliary, bronchial-alveolar and
renal tubular systems as well as islet cells of pancreas and neurons in the
central nervous systems. Sweat-gland cells, seminal vesicles and prostate
gland in the adult, as well as adipocytes and skeletal muscle cells in the
fetus were also stained. The widespread distribution of P-LAP suggests its
involvement in a variety of physiological events not restricted to the
regulation of the amounts of bioactive peptides such as arginine vasopressin
(AVP) and oxytocin (OT) in pregnancy. The presence of P-LAP in
syncytiotrophoblasts supports the idea that P-LAP in pregnancy serum is
derived from the placenta.
A 39,X/40,XY true hermaphrodite mouse with normal ovarian function
Authors: Ishikawa Hitoshi , Sakurada Kyoko , Fujita Toshiya , Yamauchi Toru
Published: January 2006

A cryptorchid mouse with a 39,X/40,XY chromosome constitution was
identified among 414 offspring born in the departmental XO mouse breeding
colony. This mouse had a small testis on the left, with no sign of
spermatogenesis, and a normal ovary on the right with several corpora lutea.
Development of four-cell hamster embryos to the blastocyst stage in vitro and its regulation by components of the culture milieu
Authors: Monis H , Bavister BD
Published: January 2006

Constituents of the culture milieu known to influence development of hamster 2-cell and 8-cell embryos were examined for effects on the 4-cell stage. Embryos were collected at the mid 4-cell stage (approx. 45-46 h after egg activation) from superovulated females and cultured for 24 h in a chemically defined medium (TLP-PVA). As with the 2-cell stage, inorganic phosphate (Pi) strongly inhibited development of 4-cell embryos, although some (14%) were able to reach the 8-cell stage or further in the presence of Pi. However, unlike 2-cell embryos, no significant inhibitory effect of glucose on development of 4-cell embryos was found. In the absence of glucose and Pi, development of 4-cell embryos was sensitive to amino acids in the medium: the mean cell number was increased using 21 amino acids compared with 4 amino acids, similarly to the 2-cell stage; however, late blastocyst development (blastocele formation) from 4-cell embryos was reduced using 21 compared with 4 amino acids, as with 8-cell embryos. Similarly to the 2-cell and 8-cell stages, raising the CO2 concentration from 5% to 10% in the gas atmosphere for culture increased the percentage of total blastocysts developing from the 4-cell stage, but did not affect the proportions of late-stage blastocysts. These data show that 4-cell-stage hamster embryos are somewhat similar to 2-cell embryos with respect to the regulation of development by constituents of the culture milieu, but, to some extent, the 4-cell embryo is a transitional stage of development.
Examination of methods for the deep freezing of goat semen
Authors: Ritar AJ , Ball PD , O'May PJ
Published: January 2006

In four experiments, freezing of goat semen in straws was examined and compared with conventional pellet-freezing. The optimum freezing regime was attained by holding straws in vapour 4 cm above liquid nitrogen for 30 s or longer, followed by plunging into liquid nitrogen. Straws exposed to vapour for only 10 s did not cool sufficiently before plunging, and cell viability was seriously impaired. Initiation of ice crystallization and the pattern of cooling of semen depended on size of straws and the type of rack used to hold straws in vapour during freezing. Nevertheless, semen was equally well stored in straws of 0.25 mL and 0.50 mL capacity and straws were most efficiently filled at 30 degrees C. Modified Tris media were used to dilute semen at rates (semen: diluent) of 1:2, 1:5, 1:11 and 1:23. Spermatozoa survived best in hypertonic diluents and deteriorated during post-thawing incubation in media of low tonicity, whilst the optimum diluent depended on rate of extension before freezing. The cooling curves differed markedly for semen frozen in straws in liquid nitrogen vapour and pellets on dry ice. Viability of spermatozoa was better for the pellet-frozen semen.
Effect of continuous infusion of oxytocin on prostaglandin F2 alpha secretion and luteolysis in the cyclic ewe
Authors: Sheldrick EL , Flint AP
Published: January 2006

Circulating concentrations of 13,14-dihydro-15-keto PGF2 alpha (DHKF2 alpha), luteinizing hormone (LH) and prolactin (PRL) have been measured in cyclic ewes treated with continuous infusions of oxytocin, in order to investigate the mechanism by which the treatment delays luteal regression. Continuous infusion of oxytocin reduced prostaglandin F2 alpha (PGF2 alpha) secretion but had no detectable direct effect on LH or PRL. Oxytocin (3 nmol h-1 i.v.) given from Day 12 or 13 until Day 18 after oestrus delayed luteolysis, eight out of nine treated ewes not returning to behavioural oestrus until Day 29.1 +/- 3.2 (mean +/- s.e.m.; cycle length of control ewes 16.7 +/- 0.3 days). In the ewe in which oxytocin failed to prevent luteolysis, luteal regression had commenced before oxytocin treatment was started. In three ewes undergoing delayed luteolysis (cycle lengths, 21, 24 and 25 days) basal concentrations of PGF2 alpha (measured as DHKF2 alpha) were unchanged, but there was only one episode of PGF2 alpha secretion compared with 20 episodes in three control ewes. Prolactin secretion was pulsatile during oxytocin infusion, and levels were low following infusion in ewes with cycle length greater than 25 days while the corpora lutea were maintained. Circulating PRL concentrations were high in ewes undergoing delayed luteolysis but there was not discrete episode of PRL secretion associated with the pre-ovulatory LH surge in these animals. To investigate the possibility that the pattern of PGF2 alpha secretion was affected by depletion of oxytocin from corpora lutea, ewes previously treated with oxytocin to delay luteolysis were given a luteolytic dose of cloprostenol on Day 21 after oestrus. The amount of oxytocin secreted in response to cloprostenol was less than 10% of that seen in ewes similarly treated on Days 11-13 after oestrus. Low levels of luteal oxytocin may therefore reduce PGF2 alpha secretion in ewes undergoing delayed luteolysis.
Sperm viability and morphology of two genetically diverse Merino lines
Authors: Lambrechts H. , van Niekerk F. E. , Cloete S. W. P. , Coetzer W. A. , van der Horst G.
Published: January 2006

Microscopically evaluated sperm parameters, as well as computer-aided sperm
motility analysis (CASMA), were used to assess sperm quality and the effect of
cryopreservation on ram semen obtained from two genetically diverse Merino
lines. These lines were divergently selected on maternal ranking values for
multiple rearing ability from the same base population since 1986.
Replacements in the high (+) line were preferentially the progeny of ewes
rearing >1 lamb per joining. Progeny of ewes rearing <1 lamb per joining
was preferred as replacements in the low (–) line. Sperm quality, as
assessed by percentages of live, abnormal and acrosome-intact spermatozoa as
well as by motility, was independent (P≤0.20) of
line, time of sampling and their interaction in ejaculated samples obtained
from the eight rams used as sires in 1995. Sperm quality of
frozen–thawed samples was adversely affected
(P≤0.01) by cryopreservation and thawing at 35˚C
for 30 s relative to fresh ejaculated samples. No consistent differences
between lines were found in epididymal sperm samples obtained from 12
slaughtered rams (6 from each line). The adverse effect
(P≤0.05) of cryopreservation and thawing at 35˚C
for 30 s on sperm viability and motility was also demonstrated for these
samples.
Marine benthic algae of Norfolk Island, South Pacific
Authors: Millar Alan J. K.
Published: January 2006

The marine benthic algae of Norfolk Island are documented and 60 of the 236
species are illustrated. All records are fully referenced, and type
localities, local distribution and notes on taxonomic and biogeographic
affinities of each species are given. Of the 236 taxa, 41 species are
Chlorophyta, 41 are Phaeophyta and the remainder (154) are Rhodophyta. Apart
from several undescribed taxa, none is endemic to the island, although
Solieria anastomosa and
Dasya fruticulosa are apparently restricted to Norfolk
and Lord Howe Island, the two islands presently sharing 106 species (almost
half the Norfolk marine flora and one-third that of Lord Howe). Although there
are some species for which Norfolk Island represents a major range extension
into or within the Pacific (Dasycladus ramosus,
Halicoryne wrightii,
Anotrichium anthericephalum,
Herposiphonia arcuata and
Polysiphonia japonica), a con- siderable number of the
species are shared with the Great Barrier Reef and the New South Wales
coastline as well as Lord Howe Island. Major northern range extensions are
recorded for the large temperate brown alga
Ecklonia radiata, and possibly
Phyllospora comosa and
Durvillaea antarctica, although the island more
typically hosts numerous tropical algae such as
Trichogloea requienii and members of the green algal
order Dasycladales including Halicoryne wrightii,
Bornetella nitida and
Neomeris annulata. As a consequence of this survey, the
two rhodymeniacean species Chrysymenia ornata and
C. digitata are considered to be conspecific.
Ceratopetalum fruits from Australian cainozoic sediments and their significance for petal evolution in the genus
Authors: Barnes Richard W. , Hill Robert S.
Published: January 2006

Ceratopetalum Sm. fruits are characterised by 4–6
enlarged woody sepals radiating from a central disk, a semi-inferior ovary,
anthers between and above each sepal and three-trace sepal venation with a
prominent intra-sepal vein. Two new species of
Ceratopetalum are described from fruits extracted from
Australian Cainozoic sediments, C. westermannii and
C. maslinensis. The presence of
Ceratopetalum in Middle Eocene Maslin Bay sediments,
South Australia, indicates a more widespread geographic distribution for the
genus during the Cenozoic. Petally is present in one extant and two fossil
species and probably represents the ancestral state despite apetally in the
oldest known fossil. Petals have probably been secondarily lost in response to
fruit specialisation or a change in pollinator vector.
A new early pleistocene species of Nothofagus and the climatic implications of co-occurring Nothofagus fossils
Authors: Jordan Gregory J.
Published: January 2006

A new species of Nothofagus,
N. pachyphylla, is proposed based on fossils from Early
Pleistocene sediments at Regatta Point, western Tasmania. This extinct species
occurred for some time with its sister species,
N. cunninghamii, which is still extant in Tasmania. The
fossil leaves of N. cunninghamii in the Regatta Point
sediments are all very small and are only consistent with leaves from cold
climate extant populations of this species. The fossil leaves of other taxa in
these sediments are also mostly at the small (and cool climate) end of the
range of the leaves of their extant relatives. These data provide
corroborating evidence for floristically based inferences of colder than
modern palaeoclimates for this fossil site. The co-occurrence of small- and
large-leaved sister species is paralleled in a number of modern Tasmanian
rainforest genera.
Nonsteroidal anti-inflammatory drugs repress β-secretase gene promoter activity by the activation of PPARγ
Authors: Sastre Magdalena , Dewachter Ilse , Rossner Steffen , Bogdanovic Nenad , Rosen Evan , Borghgraef Peter , Evert Bernd O. , Dumitrescu-Ozimek Lucia , Thal Dietmar R. , Landreth Gary , Walter Jochen , Klockgether Thomas , van Leuven Fred , Heneka Michael T.
Published: January 2006

Epidemiological evidence suggests that nonsteroidal anti-inflammatory drugs (NSAIDs) decrease the risk for Alzheimer's disease (AD). Certain NSAIDs can activate the peroxisome proliferator-activated receptor-γ (PPARγ), which is a nuclear transcriptional regulator. Here we show that PPARγ depletion potentiates β-secretase [β-site amyloid precursor protein cleaving enzyme (BACE1)] mRNA levels by increasing BACE1 gene promoter activity. Conversely, overexpression of PPARγ, as well as NSAIDs and PPARγ activators, reduced BACE1 gene promoter activity. These results suggested that PPARγ could be a repressor of BACE1. We then identified a PPARγ responsive element (PPRE) in the BACE1 gene promoter. Mutagenesis of the PPRE abolished the binding of PPARγ to the PPRE and increased BACE1 gene promoter activity. Furthermore, proinflammatory cytokines decreased PPARγ gene transcription, and this effect was supressed by NSAIDs. We also demonstrate that
in vivo
treatment with PPARγ agonists increased PPARγ and reduced BACE1 mRNA and intracellular β-amyloid levels. Interestingly, brain extracts from AD patients showed decreased PPARγ expression and binding to PPRE in the BACE1 gene promoter. Our data strongly support a major role of PPARγ in the modulation of amyloid-β generation by inflammation and suggest that the protective mechanism of NSAIDs in AD involves activation of PPARγ and decreased BACE1 gene transcription.
Generating disulfides enzymatically: Reaction products and electron acceptors of the endoplasmic reticulum thiol oxidase Ero1p
Authors: Gross Einav , Sevier Carolyn S. , Heldman Nimrod , Vitu Elvira , Bentzur Moran , Kaiser Chris A. , Thorpe Colin , Fass Deborah
Published: January 2006

Ero1p is a key enzyme in the disulfide bond formation pathway in eukaryotic cells in both aerobic and anaerobic environments. It was previously demonstrated that Ero1p can transfer electrons from thiol substrates to molecular oxygen. However, the fate of electrons under anaerobic conditions and the final fate of electrons under aerobic conditions remained obscure. To address these fundamental issues in the Ero1p mechanism, we studied the transfer of electrons from recombinant yeast Ero1p to various electron acceptors. Under aerobic conditions, reduction of molecular oxygen by Ero1p yielded stoichiometric hydrogen peroxide. Remarkably, we found that reduced Ero1p can transfer electrons to a variety of small and macromolecular electron acceptors in addition to molecular oxygen. In particular, Ero1p can catalyze reduction of exogenous FAD in solution. Free FAD is not required for the catalysis of dithiol oxidation by Ero1p, but it is sufficient to drive disulfide bond formation under anaerobic conditions. These findings provide insight into mechanisms for regenerating oxidized Ero1p and maintaining disulfide bond formation under anaerobic conditions in the endoplasmic reticulum.
Top-down facilitation of visual recognition
Authors: Bar M. , Kassam K. S. , Ghuman A. S. , Boshyan J. , Schmid A. M. , Dale A. M. , Hämäläinen M. S. , Marinkovic K. , Schacter D. L. , Rosen B. R. , Halgren E.
Published: January 2006

Cortical analysis related to visual object recognition is traditionally thought to propagate serially along a bottom-up hierarchy of ventral areas. Recent proposals gradually promote the role of top-down processing in recognition, but how such facilitation is triggered remains a puzzle. We tested a specific model, proposing that low spatial frequencies facilitate visual object recognition by initiating top-down processes projected from orbitofrontal to visual cortex. The present study combined magnetoencephalography, which has superior temporal resolution, functional magnetic resonance imaging, and a behavioral task that yields successful recognition with stimulus repetitions. Object recognition elicited differential activity that developed in the left orbitofrontal cortex 50 ms earlier than it did in recognition-related areas in the temporal cortex. This early orbitofrontal activity was directly modulated by the presence of low spatial frequencies in the image. Taken together, the dynamics we revealed provide strong support for the proposal of how top-down facilitation of object recognition is initiated, and our observations are used to derive predictions for future research.
Controlled uncoupling and recoupling of proton pumping in cytochrome
c
oxidase
Authors: Brändén Gisela , Pawate Ashtamurthy S. , Gennis Robert B. , Brzezinski Peter
Published: January 2006

Cytochrome
c
oxidase (C
c
O) is the terminal enzyme of the respiratory chain and couples energetically the reduction of oxygen to water to proton pumping across the membrane. The results from previous studies showed that proton pumping can be uncoupled from the O
2
-reduction reaction by replacement of one single residue, Asn-139 by Asp (N139D), located ≈30 Å from the catalytic site, in the D-proton pathway. The uncoupling was correlated with an increase in the p
K
a
of an internal proton donor, Glu-286, from ≈9.4 to >11. Here, we show that replacement of the acidic residue, Asp-132 by Asn in the N139D C
c
O (D132N/N139D double-mutant C
c
O) results in restoration of the Glu-286 p
K
a
to the original value and recoupling of the proton pump during steady-state turnover. Furthermore, a kinetic investigation of the specific reaction steps in the D132N/N139D double-mutant C
c
O showed that proton pumping is sustained even if proton uptake from solution, through the D-pathway, is slowed. However, during single-turnover oxidation of the fully reduced C
c
O the P → F transition, which does not involve electron transfer to the catalytic site, was not coupled to proton pumping. The results provide insights into the mechanism of proton pumping by C
c
O and the structural elements involved in this process.
Identification of the mobile light-harvesting complex II polypeptides for state transitions in
Chlamydomonas reinhardtii
Authors: Takahashi Hiroko , Iwai Masakazu , Takahashi Yuichiro , Minagawa Jun
Published: January 2006

State transition in photosynthesis is a short-term balancing mechanism of energy distribution between photosystem I (PSI) and photosystem II (PSII). When PSII is preferentially excited (state 2), a pool of mobile light-harvesting complex II (LHCII) antenna proteins is thought to migrate from PSII to PSI, but biochemical evidence for a physical association between LHCII proteins and PSI in state 2 is weak. Here, using the green alga
Chlamydomonas reinhardtii
, which has a high capacity for state transitions, we report the isolation of PSI-light-harvesting complex I (LHCI) super-complexes from cells locked into state 1 and state 2. We solubilized the thylakoid membranes with a mild detergent, separated the proteins by sucrose density gradient centrifugation, and subjected gradient fractions to gel-filtration chromatography. Three LHCII polypeptides were associated with a PSI-LHCI supercomplex only in state 2; we identified them as two minor monomeric LHCII proteins (CP26 and CP29) and one previously unreported major LHCII protein type II, or LhcbM5. These three LHCII proteins, in addition to the major trimeric LHCII proteins, were phosphorylated upon transition to state 2. The corresponding phylogenetic tree indicates that among the LHCII proteins associated with PSII, these three LHCII proteins are the most similar to the LHC proteins for PSI (LHCI). Our results are important because CP26, CP29, and LhcbM5, which have been viewed as belonging solely to the PSII complex, are now postulated to shuttle between PSI and PSII during state transitions, thereby acting as docking sites for the trimeric LHCII proteins in both PSI and PSII.