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At least 919 records · Page 51Linked to original sources

PubMed2007

Noggin signaling from Xenopus animal blastomere lineages promotes a neural fate in neighboring vegetal blastomere lineages.

In Xenopus, localized factors begin to regionalize embryonic fates prior to the inductive interactions that occur during gastrulation. We previously reported that an animal-to-vegetal signal that occurs prior to gastrulation promotes primary spinal neuron fate in vegetal equatorial (C-tier) blastomere lineages. Herein we demonstrate that maternal mRNA encoding noggin is enriched in animal tiers and at low concentrations in the C-tier, suggesting that the neural fates of C-tier blastomeres may be responsive to early signaling from their neighboring cells. In support of this hypothesis, experimental alteration of the levels of Noggin from animal equatorial (B-tier) or BMP4 from vegetal (D-tier) blastomeres significantly affects the numbers of primary spinal neurons derived from their neighboring C-tier blastomeres. These effects are duplicated in blastomere explants isolated at cleavage stages and cultured in the absence of gastrulation interactions. Co-culture with animal blastomeres enhanced the expression of zygotic neural markers in C-tier blastomere explants, whereas co-culture with vegetal blastomeres repressed them. The expression of these markers in C-tier explants was promoted when Noggin was transiently added to the culture during cleavage/morula stages, and repressed with the transient addition of BMP4. Reduction of Noggin translation in B-tier blastomeres by antisense morpholino oligonucleotides significantly reduced the efficacy of neural marker induction in C-tier explants. These experiments indicate that early anti-BMP signaling from the animal hemisphere recruits vegetal equatorial cells into the neural precursor pool prior to interactions that occur during gastrulation.

Animals↗

PubMed1993

Effect of lithium on ionic balance and polyphosphoinositide metabolism during larval vegetalization of the sea urchin Paracentrotus lividus.

Treatment of Paracentrotus lividus embryos with lithium, which is known to block the polyphosphoinositide (PPI) cycle, induces their development into vegetalized larvae. We have investigated how ionic balance and PPI metabolism were affected in such vegetalized embryos. Exposure to 80 mM lithium for 3 1/2 hr at the morula stage induced an accumulation of lithium into the embryos, concomitant with a decrease in intracellular sodium and potassium contents. Intracellular lithium was totally expelled 6 hr after removal of this ion from the external medium. We found that intracellular levels of all PPI-cycle intermediates were altered after vegetalization: PIP2 and PIP increased, while PI decreased. Finally, vegetalized embryos showed a significant depression of IP3 mass. The degree of change in inositol phosphates increased as the intracellular accumulation of lithium increased. The change in morphology (vegetalization) also correlated well with the increase in lithium accumulation. This is consistent with the hypothesis that lithium alters the PPI cycle.

Animals↗

PubMed1998

Additional vegetative growth in maize reflects expansion of fates in preexisting tissue, not additional divisions by apical initials.

The maize shoot is usually determinate: the apical meristem produces a fixed number of vegetative nodes before it switches to tassel development. Culturing maize meristems, however, delays their determinacy. Cultured meristems may form up to twice the usual number of vegetative nodes. Clonal analysis of the "extra" vegetative nodes reveals that these nodes are the product of conversion, roughly equivalent to a homoeotic transformation, of tissue that otherwise would form the base of the tassel. Altered activity of the apical initials does not generate the extra vegetative growth. The conserved, stereotypical activity of the apical initials even in the face of radically prolonged vegetative growth suggests that apical initials in this annual grass may acquire a highly restricted fate (presporogenous tissue) early in embryogenesis.

Cell Count↗

PubMed2001

VegT activation of Sox17 at the midblastula transition alters the response to nodal signals in the vegetal endoderm domain.

In Xenopus, the prospective endoderm and mesoderm are localized to discrete, adjacent domains at the beginning of gastrulation, and this is made evident by the expression of Sox17 in vegetal blastomeres and Brachyury (Xbra) in marginal blastomeres. Here, we examine the regulation of Sox17alpha expression and the role of Sox17alpha in establishing the vegetal endodermal gene expression domain. Injection of specific inhibitors of VegT or Nodal resulted in a loss of Sox17alpha expression in the gastrula. However, the onset of Sox17alpha expression at the midblastula transition was dependent on VegT, but not on Nodal function, indicating that Sox17alpha expression is initiated by VegT and then maintained by Nodal signals. Consistent with these results, VegT, but not Xenopus Nodal-related-1 (Xnr1), can activate Sox17alpha expression at the midblastula stage in animal explants. In addition, VegT activates Sox17alpha in the presence of cycloheximide or a Nodal antagonist, suggesting that Sox17alpha is an immediate-early target of VegT in vegetal blastomeres. Given that Nodal signals are necessary and sufficient for both mesodermal and endodermal gene expression, we propose that VegT activation of Sox17alpha at the midblastula transition prevents mesodermal gene expression in response to Nodal signals, thus establishing the vegetal endodermal gene expression domain. Supporting this idea, Sox17alpha misexpression in the marginal zone inhibits the expression of multiple mesodermal genes. Furthermore, in animal explants, Sox17alpha prevents the induction of Xbra and MyoD, but not Sox17beta or Mixer, in response to Xnr1. Therefore, VegT activation of Sox17alpha plays an important role in establishing a region of endoderm-specific gene expression in vegetal blastomeres.

Animals↗

PubMed1984

Cyclic-AMP content and trehalase activation in vegetative cells and ascospores of yeast.

Addition of glucose to yeast ascospores, glucose-grown vegetative cells from the stationary growth-phase or acetate-grown vegetative cells from the logarithmic growth-phase induces a rapid tenfold increase in the activity of trehalase. Trehalase activation is followed by a period of slow inactivation. It was possible to reverse the inactivation in the presence of glucose in all cell types immediately and completely by subsequent addition of a nitrogen source. This reactivation by nitrogen sources is in disagreement with proteolytic breakdown being responsible for trehalase inactivation in the presence of glucose. The addition of glucose induced in all cell types a rapid transient increase of the cellular cyclic-AMP content. In ascospores the increase of the cyclic-AMP level was about twofold, in glucose-grown stationary-phase vegetative cells four- to fivefold and in acetate-grown vegetative cells about sevenfold. Subsequent addition in the presence of glucose of a nitrogen source caused a new twofold increase of the cyclic-AMP level in ascospores. In the other two cell types however addition of a nitrogen source after the initial transient increase of the cyclic-AMP level did not produce a significant new increase. Although the data obtained for ascospores at first seemed to confirm the crucial role of the increase in the cyclic-AMP level for the activation of trehalase, the data obtained afterwards for vegetative cells indicated that it is possible to activate trehalase in yeast without a concomitant increase of the total cellular cyclic-AMP content.

Cyclic AMP↗

PubMed1988

Prognosis of the posttraumatic vegetative state.

Of 1373 patients who, following severe brain injury had been comatose for over 6 hours, 140 (10%) were in a vegetative state one month later. Fifty-nine regained consciousness but none of those aged over 40 became independent during the first year. Of those still in a vegetative state after 3 months, none became independent irrespective of age. Of all patients comatose for over 6 hours after severe brain injury, only 1% was in a vegetative state after one year. Certain scores for features such as age, pupillary reactions, eye-opening and eye movements indicate either a favourable prognosis, a fatal outcome or irreversible coma. It is only in some 10% of all patients in coma or in a vegetative state during the first two weeks after the accident that it is possible to predict with a high degree of probability (p greater than 0.95), an unfavourable outcome (death or irreversible coma) within one year. At no time after the onset of coma is it possible to predict or distinguish, with a fair degree of probability (e.g. p greater than 0.80), those patients who will remain in a vegetative state from those who will die.

Adult↗

PubMed2002

Impact of selective herbicide right-of-way vegetation treatment on birds.

Power line rights-of-way provide a major portion of the shrub habitat in New York. Since this habitat type is on the decline, many of the birds dependent on shrub habitat are also declining. The methods used to control right-of-way vegetation could therefore have serious impacts on several birds of conservation concern. Since New York is increasingly using selective herbicide treatments in vegetation management, we sought to investigate the potential impacts of these treatments on nesting birds. The study looked at plots in two adjacent rights-of-way before and after a selective herbicide treatment in one of the rights-of-way. We investigated three bird species: alder flycatcher (Empidonax alnorum), chestnut-sided warbler (Dendroica pensylvanica), and gray catbird (Dumetella carolinensis). All three species exhibited a preference for shrub vegetation around nest sites. The selective herbicide treatment did not significantly decrease that shrub vegetation, and neither the density nor the nesting success of the three species declined following the treatment. We conclude that selective herbicide vegetation management encourages the development of shrub habitat without negatively impacting the birds nesting in the habitat.

Animals↗

PubMed1998

Short-Term Influence of Tank Tracks on Vegetation and Microphytic Crusts in Shrubsteppe Habitat

/ I examined vegetation and microphytic crust cover on two sites in burned and two sites in unburned big sagebrush (Artemisia tridentata Nutt.) habitat within the Idaho Army National Guard Orchard Training Area in southwestern Idaho. The purpose of this study was to determine the short-term (1-2 years) influence of tank tracks on vegetation and microphytic crusts in shrubsteppe habitat. The two types of tank tracks studied were divots (area where one track has been stopped or slowed to make a sharp turn) and straight-line tracks. Divots generally had a stronger influence on vegetation and microphytic crusts than did straight-line tracks. Tank tracks increased cover of bare ground, litter, and exotic annuals, and reduced cover of vegetation, perennial native grasses, sagebrush, and microphytic crusts. Increased bare ground and reduced cover of vegetation and microphytic crusts caused by tank tracks increase the potential for soil erosion and may reduce ecosystem productivity. Reduced sagebrush cover caused by tank tracks may reduce habitat quality for rodents. Tank tracks may also facilitate the invasion of exotic annuals into sagebrush habitat, increasing the potential for wildfire and subsequent habitat degradation. Thus, creation of divots and movement through sagebrush habitat by tanks should be minimized.KEY WORDS: Divots; Fire history; Idaho; Military; Sagebrush; Straight-line tracks

Journal Article↗

PubMed1999

FORUM: A Suggestion for an Improved Vegetation Scheme for Local and Global Mapping and Monitoring.

/ Understanding of global ecological problems is at least partly dependent on clear assessments of vegetation change, and such assessment is always dependent on the use of a vegetation classification scheme. Use of satellite remotely sensed data is the only practical means of carrying out any global-scale vegetation mapping exercise, but if the resulting maps are to be useful to most ecologists and conservationists, they must be closely tied to clearly defined features of vegetation on the ground. Furthermore, much of the mapping that does take place involves more local-scale description of field sites; for purposes of cost and practicality, such studies usually do not involve remote sensing using satellites. There is a need for a single scheme that integrates the smallest to the largest scale in a way that is meaningful to most environmental scientists. Existing schemes are unsatisfactory for this task; they are ambiguous, unnecessarily complex, and their categories do not correspond to common-sense definitions. In response to these problems, a simple structural-physiognomically based scheme with 23 fundamental categories is proposed here for mapping and monitoring on any scale, from local to global. The fundamental categories each subdivide into more specific structural categories for more detailed mapping, but all the categories can be used throughout the world and at any scale, allowing intercomparison between regions. The next stage in the process will be to obtain the views of as many people working in as many different fields as possible, to see whether the proposed scheme suits their needs and how it should be modified. With a few modifications, such a scheme could easily be appended to an existing land cover classification scheme, such as the FAO system, greatly increasing the usefulness and accessability of the results of the landcover classification. KEY WORDS: Vegetation scheme; Mapping; Monitoring; Land cover

Journal Article↗

PubMed2004

Vegetable crop management strategies to increase the quantity of phytochemicals.

BACKGROUND: Numerous epidemiological studies show an inverse association between vegetable consumption and chronic diseases such as different types of cancer and cardiovascular disease. Phytochemicals in vegetables are known to be responsible for this observed protective effect. Therefore, raising the levels of these health-promoting substances in vegetables and/or using phytochemicals as food supplements would be desirable especially since dietary behaviour and the suboptimal efficiency of diet campaigns in industrial nations of Northern Europe and North America have resulted in a relatively low increase of vegetable consumption. AIM OF THE STUDY: The aim of this paper is to suggest crop management strategies based on genotypic and ecophysiological effects for the production of vegetables enriched with phytochemicals which can be served as fresh market products or be used as raw material for functional foods and supplements. RESULTS: Crop management strategies, representatively given here with broccoli, cauliflower and radish, demonstrated that the contents of individual phytochemicals could be increased 10-fold in broccoli and cauliflower, and 2-fold in radish.

Agriculture↗

PubMed2006

Fire does not alter vegetation in infertile prairie.

The paradigm in prairie ecology is that fire is one of the key factors determining vegetation composition. Fire can impact grassland ecosystems in various ways, including changing plant species composition and inducing nitrogen loss. I found that 17 years of different burning frequencies in infertile grassland had only a minor impact on the vegetation composition and diversity. The only major impact from increasing the frequency of fires was a decrease of Poa pratensis abundance. However, other plant species did not respond to the change in Poa abundance. This result contrasts with previous studies in savannas and more productive grasslands, where the balance between trees, grasses, and the elimination of the litter layer can result in large vegetation changes. However, in this system primary productivity was low, litter did not accumulate and no major vegetation shifts occurred. Thus, the long-term vegetation impacts of burning in an infertile, low-productivity prairie were minimal.

Analysis of Variance↗

PubMed2003

West-east contrast of phenology and climate in northern Asia revealed using a remotely sensed vegetation index.

The phenology of the vegetation covering north Asia (mainly Siberia) and its spatial characterstics were investigated using remotely sensed normalized difference vegetation index (NDVI) data. The analysis used the weekly averaged NDVI over 5 years (1987-1991) using the second-generation weekly global vegetation index dataset (0.144 degrees x 0.144 degrees spatial resolution). In the seasonal NDVI cycle, three phenological events were defined for each pixel: green-up week (NDVI exceeds 0.2), maximum week, and senescence week (NDVI drops below 0.2). Generally there was a west-early/east-late gradient in the three events in north Asia. In the zonal transect between 45 degrees and 50 degrees N, the timing of green-up, maximum, and senescence near 60 degrees E (Kazakh) was about 3.4, 8.7, and 13.4 weeks earlier than near 110 degrees E (Mongolia) respectively. It has been suggested that vegetation near Kazakh only flourishes during a short period when water from snow melt is available from late spring to early summer. In Mongolia, abundant water is available for the vegetation, even in midsummer, because of precipitation. In the 50-60 degrees N zonal transect, the green-up and maximum near 40 degrees E were about 3.8 and 3.9 weeks earlier than near 115 degrees E, respectively. As for the week of senescence, there was no clear west-east trend. This west-to-east phenological gradient was related to the weekly cumulative temperature (over 0 degrees C). Weeks in which the cumalative temperature exceeded 40 degrees C and 140 degrees C had a similar west-east distribution to green-up and maximum NDVI.

Asia↗

PubMed2003

Resprouting ability of Quercus crispula seedlings depends on the vegetation cover of their microhabitats.

To examine the effects of vegetation cover on the resprouting abilities of Quercus crispula seedlings, in each of three consecutive years, we artificially clipped seedlings growing in microhabitats with differing degrees of vegetation cover. We also investigated the relationship between the level of total nonstructural carbohydrate (TNC) and resprouting ability. Seedlings with clipped shoots in gaps produced larger resprouting shoots than those in the understory. Moreover, both the percentage of resprouting seedlings and the survival ratio in seedlings with clipped shoots were negatively correlated with the degree of vegetation cover. Seedlings stored high levels of TNC, especially in their roots, and their TNC levels were negatively correlated with the degree of vegetation cover. There were also positive relationships between the TNC levels in their roots and the degree of resprouting. Hence, we conclude that release from vegetation cover enhanced the resprouting ability of Q. crispula seedlings by increasing their levels of stored carbohydrate. The key variables affected were the resprouting ratio (the proportion of seedlings capable of producing new shoots) and the size of the resprouted shoots.

Biomass↗

PubMed1979

Serial echocardiographic appearance of healing bacterial vegetations.

Serial M mode and cross-sectional echocardiograms were obtained from six patients who had been treated with antibiotic drugs for infectious endocarditis. Three to six M mode echocardiograms and one to six cross-sectional echocardiograms were obtained from each patient over a follow-up period averaging 50 weeks (range 10 to 108 weeks). On echocardiography, vegetations were observed to have become smaller and more echo-reflective with healing. A dramatic change was seen in two patients after peripheral embolization. M mode echocardiography was particularly helpful in determining the quality of echo reflection by vegetations; cross-sectional echocardiography was more helpful in judging the size and shape of a vegetation. Echocardiography is ideally suited for the serial visualization of healing vegetations in patients who do not require early valve replacement. It may prove helpful to examine serially valve vegetations with both M mode and cross-sectional echocardiography when following up patients with infectious endocarditis treated with antibiotic agents.

Adult↗

PubMed1981

Noninvasive methods for detection of valve vegetations in infective endocarditis.

To determine the optimal noninvasive method for the demonstration of endocarditic vegetations, 35 consecutive episodes of clinically diagnosed endocarditis in 33 patients were studied with M mode and two dimensional echocardiography, and with gallium-67 citrate and technetium-99m stannous pyrophosphate cardiac scanning. Clinical criteria for the diagnosis of endocarditis were: temperature higher than 38 degrees C; sustained bacteremia with at least three positive blood cultures; no extracardiac focus of bacteremia; and known underlying heart disease, a new or changing murmur or a history of intravenous drug abuse with radiologic evidence of septic pulmonary emboli. M mode echocardiography detected 18 vegetations in 17 of the 35 episodes of endocarditis studied (49 percent positive); two dimensional echocardiography detected 30 vegetations in 28 of the 35 episodes studied (80 percent positive). In contrast, no vegetations were detected with technetium-99m stannous pyrophosphate scanning,, and only two gallium-67 citrate scans were positive. The advantage of the two dimensional echocardiographic technique over all others tested was particularly notable for the identification of aortic and tricuspid valve vegetations.

Adolescent↗

PubMed1988

Ultraviolet light induces different spectra of lacI sequence changes in vegetative and conjugating cells of Escherichia coli.

We have analyzed the nucleotide sequence changes responsible for mutations from lacIs to lacI- induced in ultraviolet light-irradiated, excision-deficient cells. Irradiated cells were either used as donors in the conjugational transfer of an F' lacIs plasmid to SOS-induced, excision-deficient recipients or allowed to continue vegetative growth. Although the types and proportions of premutagenic lesions are likely to have been very similar in these two circumstances, analysis of the sequence data shows that different spectra of mutations were induced. In vegetative cells there were about equal numbers of transitions and transversions, but transitions outnumbered transversions by about three to one in exconjugants. About 90% of the single nucleotide substitutions could be assigned to a bipyrimidine target sequence in both sets of data, but they differed with respect to the location of the substitution: more or less equal numbers were found at the 3' and 5' sites of the probable bipyrimidine target in vegetative cells, but in exconjugants over 80% were at the 3' site. It is also possible that mutations were targeted more commonly at T-C sequences in exconjugants than in vegetative cells, but the evidence for this is less secure. We conclude that these results reflect some dissimilarity between vegetative cells and exconjugants in the way damaged DNA is replicated or lesions tolerated, but the particular features of these processes responsible for the different mutational spectra have not yet been identified.

Base Sequence↗

PubMed1991

The importance of soil adhered to vegetation as a source of radionuclides ingested by grazing animals.

Soil ingestion has been identified as a potentially important source of radionuclides to grazing animals. Seasonal patterns of soil adherence to vegetation and its implications for the radionuclide intake of grazing animals were measured at two west Cumbrian sites. Soil adhesion to vegetation was highly seasonal, being highest in autumn and winter. At Site 1 (a lowland pasture close to the British Nuclear Fuels plc Sellafield Reprocessing Plant, Cumbria, UK), vegetation samples were found to consist of up to 46% soil (by dry weight). Therefore, the importance of soil as a potential source of radionuclides to grazing animals was also seasonal; soil comprised up to 92% of the 137Cs and potentially all of the 239/240Pu of vegetation samples at Site 1 and up to 62% of the 137Cs at Site 2 (an upland farm contaminated following the Chernobyl accident). Analyses of sheep faecal samples confirmed the seasonal importance of soil as a potential source of radionuclides. The importance of soil adhering to vegetation, as a source of contaminant 137Cs, increased with time after the Chernobyl accident. Calculations of soil ingestion must be made when the intake of radionuclides by grazing animals is being studied. In some circumstances, present radioecological models may considerably underestimate the importance of soil ingestion.

Accidents↗

PubMed2004

Testing the ecotoxicology of vegetable versus mineral based lubricating oils: 2. Induction of mixed function oxidase enzymes in barramundi, Lates calcarifer, a tropical fish species.

An increasing number of vegetable-based oils are being developed as environmentally friendly alternatives to petroleum products. However, toxicity towards key tropical marine species has not been investigated. In this study we used laboratory-based biomarker induction experiments to compare the relative stress of a vegetable-based lubricating oil for marine 2-stroke engines with its mineral oil-based counterpart on tropical fish. The sub-lethal stress of 2-stoke outboard lubricating oils towards the fish Lates calcarifer (barramundi) was examined using liver microsomal mixed function oxidase (MFO) induction assays. This study is the first investigation into the use of this key commercial species in tropical North Queensland, Australia in stress assessment of potential hydrocarbon pollution using ethoxyresorufin O-deethylase (EROD) induction. Our results indicated that barramundi provide a wide range of inducible rates of EROD activity in response to relevant organic stressors. The vegetable- and mineral-based lubricants induced significant EROD activity at 1.0 mg kg(-1) and there was no significant difference between the two oil treatments at that concentration. At increasing concentrations of 2 and 3 mg kg(-1), the mineral-based lubricant resulted in slightly higher EROD activity than the vegetable-based lubricant. The EROD activity of control and treated barramundi are found to be within ranges for other species from temperate and tropical environments. These results indicate that vegetable-based lubricants may be less stressful to barramundi than their mineral counterparts at concentrations of lubricant > or =2 mg kg(-1). There is great potential for this species to be used in the biomonitoring of waterways around tropical North Queensland and SE Asia.

Animals↗