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PubMed1993

Isotypic analysis of grass-pollen-specific immunoglobulins in human plasma. 2. Quantification of the IgE, IgM, IgA class and the IgG subclass antibodies.

Previously, the specificity of human immune responses to Dactylis pollen was analyzed in 26 plasma samples with high levels of grass-pollen-specific IgG4 ('IgG4+ plasma', largely from grass-pollen-allergic patients), as compared to 25 plasma samples with low grass-pollen-specific IgG4 ('normal plasma', from nonatopic individuals). In the present study, a quantification of the Dactylis-pollen-specific IgE, IgM, IgA class and IgG subclass antibodies in these plasma samples is proposed. Isotypic distribution in IgG4+ plasma was 68% IgG [IgG2 (38%) > IgG4 (30%) > IgG1 (19%) > IgG3 (13%)], 27% IgM, 4% IgA and 0.05% IgE. In normal plasma it was 73% IgM, 20% IgG [IgG3 (38%) > IgG2 (33%) > IgG1 (29%) > IgG4 (0%)], 6% IgA and 0.006% IgE. In IgG4+ plasma, specific IgE, IgG1, IgG2 and IgG4 concentrations were positively correlated between each other. Finally, the present study clearly confirmed the possible role of the CH gene regulation in allergic diseases.

Gene Expression Regulation↗
PubMedDate not supplied

Diagnostic value of total IgE and antigen specific IgE using RAST in pollenosis.

41 patients with clinically demonstrated pollinosis are studied. The following test were performed on all of them: a) Intradermal skin tests using grass pollen extracts (Pangramin III) and with extracts of Dactylis glomerate, Lollium perenne and Poa pratensis. b) Totol serum IgE determination. c) Antigen specific IgE (RAST) determination against the pollens mentioned in b). d) Passive hemagglutination against the pollen Dactylis glomerate. Basing on the results obtained, we have arrived to the following conclusions: 1) IgE determination with intensely positive intradermal skin tests in all cases, gave the following data: 27.5% normal values, 35% slightly elevated and 37.5% highly increased values. We believe that IgE determination can only be used to estimate the "allergization" degree of the patient. 2) No relation between the antigen concentration used in the intradermal skin test, and serum IgE concentration was found. 3) Taking in consideration that the antigen extracts used for RAST and intradermal skin tests were obtained from different sources (Sweden and Spain, respectively), the relation between both determinations ranged between 52.5% and 60%, in a total of 123 tests performed. 4) Considering that in the allergic response antibodies other than reagins (IgG) take part, and taking into account the results obtained with the passive hemagglutination technique, we consider that this last method should be included as a diagnostic routine tool in the pollinic patient.

Adolescent↗
PubMed2003

[In vitro effects of antiallergic eyedrops on complement activation induced by particulate matter].

BACKGROUND: Recent decades have been marked by an increasing number of patients suffering from ocular allergic-like symptoms without being associated with an increase in IgE levels. These symptoms include heaviness of the lid, foreign body sensation, burning, stinging and photophobia. Both epidemiological studies and controlled human exposure clinical studies have shown cause-effect relationships between allergic-like symptoms and environmental factors such as outdoor air pollutants or poor indoor air quality. An ocular surface subclinical inflammation is thought to be responsible for pseudoallergic, pollution-related conjunctivitis. The complement system is considered as one of the major effector mechanisms involved in initiation of the subclinical inflammation that leads to IgE-independent eye irritation. PURPOSE: To study the capability of nine antiallergic eyedrops commonly used in the treatment of allergic conjunctivitis to inhibit complement activation induced in vitro by pollutants. METHODS: Normal human serum obtained from healthy individuals was used as a source of complement. Activation of complement was assessed using the complement hemolytic 50% (CH50) assay, in the absence or the presence of antiallergic eyedrops and in the absence or the presence of various stimuli, including sand, common house dust, eye mascara, and Dactylis glomerata pollen extract. Zymosan was used as a standardized complement activator. The following eyedrops were studied: Naabak (4.9% N-acetyl aspartic acid-glutamic acid, NAAGA, sodium salt), Almide (lodoxamide 0.1%), Levophta (0.05% levocabastine), Emadine (0.05% emedastine), Tilavist (2% nedocromil), Allergodil (0.05% azelastine), Patanol (olopatadine), and Zaditen (0.025% ketotifen). Effects of preservative-free lodoxamide and ketotifen were also assessed and compared to those of the preserved formulations. A solution of 0.01% benzalkonium chloride (BAC), the most widely used preservative in topical eyedrops, was also tested. RESULTS: Zymosan-induced activation of complement (30+/-6%) was significantly lowered by preincubation of serum with unpreserved NAAGA (16.6+/-4%, p=0.0026) or benzalkonium-preserved nedocromil (20+/-2%, p=0.022). Preserved levocabastine, emedastine, olopatadine and ketotifen did not interfere with zymosan-induced complement activation, whereas preserved azelastine, lodoxamide and benzalkonium chloride significantly aggravated complement activation induced by zymosan. Similar results were obtained when complement activation was triggered by sand, common house dust, mascara, or by an allergenic extract of Dactylis glomerata pollen. In the absence of complement activator, none of the antiallergic eyedrops induced a significant change in CH50 titer, indicating that the deleterious pro-inflammatory effect of preserved azelastine and lodoxamide may occur only once complement activation has been initiated, i.e., on an inflamed ocular surface. CONCLUSION: Among the antiallergic eyedrops tested in this study, only Naabak and Tilavist were found to significantly inhibit complement activation triggered by particulate matters or pollen allergenic extract. Such an anticomplement activity confers these two molecules a potential in the therapeutic management of pollution-related pseudoallergic conjunctivitis.

Air Pollutants↗
PubMed2003

[Effects of grazing, cutting and decapitating on grass populations on the artificial grassland in subtropical zone of China].

Studies on the effects of grazing, cutting and decapitating on grass populations on the artificial grassland in the subtropical zone of China showed that moderate grazing and cutting could increase the adaptability of Dactylis glomerata and Lolium prenn due to decapitating. Decapitating could rescind the apical dominance and reproduction growth of grass, and hence, the ecological effects of grazing and cutting on grass could be realized by decapitating, and the population density, caloric value and energy accumulation of Dactylis glomerata and Lolium prenn increased obviously. Apical dominance of grasses could lower the population density, energy accumulation and intra-population competitive ability.

Animal Feed↗
PubMed2002

Roles of the plasma membrane and the cell wall in the responses of plant cells to freezing.

In an effort to clarify the responses of a wide range of plant cells to freezing, we examined the responses to freezing of the cells of chilling-sensitive and chilling-resistant tropical and subtropical plants. Among the cells of the plants that we examined, those of African violet ( Saintpaulia grotei Engl.) leaves were most chilling-sensitive, those of hypocotyls in mungbean [ Vigna radiata (L.) R. Wilcz.] seedlings were moderately chilling-sensitive, and those of orchid [ Paphiopedilum insigne (Wallich ex Lindl.) Pfitz.] leaves were chilling-resistant, when all were chilled at -2 degrees C. By contrast, all these plant cells were freezing-sensitive and suffered extensive damage when they were frozen at -2 degrees C. Cryo-scanning electron microscopy (Cryo-SEM) confirmed that, upon chilling at -2 degrees C, both chilling-sensitive and chilling-resistant plant cells were supercooled. Upon freezing at -2 degrees C, by contrast, intracellular freezing occurred in Saintpaulia leaf cells, frost plasmolysis followed by intracellular freezing occurred in mungbean seedling cells, and extracellular freezing (cytorrhysis) occurred in orchid leaf cells. We postulate that chilling-related destabilization of membranes might result in the loss of the ability of the plasma membrane to act as a barrier against the propagation of extracellular ice in chilling-sensitive plant cells. We also examined the role of cell walls in the response to freezing using cells in which the plasma membrane had been disrupted by repeated freezing and thawing. In chilling-sensitive Saintpaulia and mungbean cells, the cells with a disrupted plasma membrane responded to freezing at -2 degrees C by intracellular freezing. By contrast, in chilling-resistant orchid cells, as well as in other cells of chilling-resistant and freezing-resistant plant tissues, including leaves of orchard grass ( Dactylis glomerata L.), leaves of Arabidopsis thaliana (L.) Heynh. and cortical tissues of mulberry ( Morus bombycis Koids.), cells with a disrupted plasma membrane responded to freezing by extracellular freezing. Our results indicate that, in the chilling-sensitive plants cells that we examined, not only the plasma membrane but also the cell wall lacked the ability to serve as a barrier against the propagation of extracellular ice, whereas in the chilling-resistant plant cells that we examined, not only the plasma membrane but also the cell wall acted as a barrier against the propagation of extracellular ice. It appears, therefore, that not only the plasma membrane but also the cell wall greatly influences the freezing behavior of plant cells.

Acclimatization↗
PubMed2003

Human serum IgE-mediated mast cell degranulation shows poor correlation to allergen-specific IgE content.

BACKGROUND: Although allergen-specific IgE content in serum can be determined immunochemically, little is known about the relationship between this parameter and the strength of the degranulation response upon allergen triggering. OBJECTIVES: Analyse the degranulation capacity of immunochemically defined purified and serum IgE after challenge with anti-IgE or allergen using a rat mast cell line (RBL) transfected with the alpha-chain of the human high-affinity IgE receptor (FcepsilonRI). METHODS: Purified IgE specific for 4-hydroxy-3nitrophenylacetyl, purified IgE of unknown specificity, and sera from allergic patients sensitive to Dermatophagoides pteronyssinus and Dactylis glomerata were assessed. Degranulation was measured by a beta-hexosaminidase release assay after anti-IgE or allergen-specific challenge. RESULTS: For purified monoclonal IgE a significant correlation (r = 0.97) was found between the proportion of bound allergen-specific IgE and the strength of the degranulation response. In contrast, no correlation (r = 0.27) was detected after sensitization with serum IgE. CONCLUSION: Our studies demonstrate that mast cell activation mediated through IgE from allergic patients is a result of complex relationships that are not only dependent on allergen-specific IgE content but also relate to the capacity to efficiently sensitize and trigger the signalling responses that lead to degranulation.

Allergens↗
PubMed2003

Vertical leaf nitrogen distribution in relation to nitrogen status in grassland plants.

Vertical gradients of leaf nitrogen (N) per unit leaf area (NLA) are viewed as plastic responses that optimize N utilization with respect to carbon assimilation. However, it has been shown that plant species, sowing density and N availability affect the steepness of the NLA gradient relative to the photon flux density (PFD) gradient. This paper tests the hypothesis that such variation is related to the N status of the plant. The N status was analysed using the concept of the critical N concentration (Ncrit) in which shoot N per unit dry mass (NSM) decreases with shoot mass, and a negative deviation of actual NSM from Ncrit indicates N shortage in the plant. The hypothesis was tested with contrasting grassland species Medicago sativa, Dactylis glomerata and Taraxacum officinale by varying PFD and N availability, plant density and hierarchical positions of individuals within stands. Combinations of all treatments showed a general negative correlation between the N allocation coefficient (i.e. the slope of the NLA-PFD relationship) and NSM for all three species. Thus, NLA, relative to PFD, gradients became steeper with increasing shoot mass and increasing N shortage in the plant. These data are consistent with the view that internal N availability is an important factor in modifying the NLA gradient.

Biomass↗
PubMed2003

Oxygen deficiency affects carbohydrate reserves in overwintering forage crops.

Anaerobic conditions developing under an ice cover affect winter survival and spring regrowth of economically important perennial crops. The objective was to compare, during a prolonged period of low (<2%) O2 at low temperature, the concentration of carbohydrates of four plant species contrasting in their resistance to oxygen deficiency. Four perennial forage species, lucerne (Medicago sativa L.), red clover (Trifolium pratense L.), timothy (Phleum pratense L.), and cocksfoot (Dactylis glomerata L.) were subjected to a progressively developing oxygen deficiency stress by enclosing potted plants in gas-tight bags in late autumn for overwintering in an unheated greenhouse. Timothy was previously reported to be more resistant to oxygen deficiency than the three other species. Non-structural carbohydrates increased and remained at a higher concentration in timothy than in the other three species under low O2 concentration. Concentrations of sucrose, fructose, glucose, and fructans increased in response to oxygen deficiency in timothy, whereas the concentration of soluble sugars decreased under the same conditions in lucerne, red clover, and cocksfoot. The gene expression of glyceraldehyde-3-phosphate dehydrogenase increased in response to low oxygen concentration in oxygen deficiency-sensitive lucerne while it remained unchanged in the oxygen deficiency-resistant timothy. It is concluded that timothy maintains higher carbohydrate reserves under oxygen deficiency, a specific feature that could favour its winter survival and spring regrowth.

Carbohydrate Metabolism↗
PubMed2006

Effects of management regime and plant species on the enzyme activity and genetic structure of N-fixing, denitrifying and nitrifying bacterial communities in grassland soils.

Management by combined grazing and mowing events is commonly used in grasslands, which influences the activity and composition of soil bacterial communities. Whether observed effects are mediated by management-induced disturbances, or indirectly by changes in the identity of major plant species, is still unknown. To address this issue, we quantified substrate-induced respiration (SIR), and the nitrification, denitrification and free-living N(2)-fixation enzyme activities below grass tufts of three major plant species (Holcus lanatus, Arrhenatherum elatius and Dactylis glomerata) in extensively or intensively managed grasslands. The genetic structures of eubacterial, ammonia oxidizing, nitrate reducing, and free-living N(2)-fixing communities were also characterized by ribosomal intergenic spacer analysis, and denaturing gradient gel electrophoresis (DGGE) or restriction fragment length polymorphism (RFLP) targeting group-specific genes. SIR was not influenced by management and plant species, whereas denitrification enzyme activity was influenced only by plant species, and management-plant species interactions were observed for fixation and nitrification enzyme activities. Changes in nitrification enzyme activity were likely largely explained by the observed changes in ammonium concentration, whereas N availability was not a major factor explaining changes in denitrification and fixation enzyme activities. The structures of eubacterial and free-living N(2)-fixing communities were essentially controlled by management, whereas the diversity of nitrate reducers and ammonia oxidizers depended on both management and plant species. For each functional group, changes in enzyme activity were not correlated or were weakly correlated to overall changes in genetic structure, but around 60% of activity variance was correlated to changes in five RFLP or DGGE bands. Although our conclusions should be tested for other ecosystems and seasons, these results show that predicting microbial changes induced by management in grasslands requires consideration of management-plant species interactions.

Agriculture↗
PubMed2004

Surfactant protein D increases phagocytosis and aggregation of pollen-allergen starch granules.

Recent studies have shown that surfactant components, in particular the collectins surfactant protein (SP)-A and -D, modulate the phagocytosis of various pathogens by alveolar macrophages. This interaction might be important not only for the elimination of pathogens but also for the elimination of inhaled allergens and might explain anti-inflammatory effects of SP-A and SP-D in allergic airway inflammation. We investigated the effect of surfactant components on the phagocytosis of allergen-containing pollen starch granules (PSG) by alveolar macrophages. PSG were isolated from Dactylis glomerata or Phleum pratense, two common grass pollen allergens, and incubated with either rat or human alveolar macrophages in the presence of recombinant human SP-A, SP-A purified from patients suffering from alveolar proteinosis, a recombinant fragment of human SP-D, dodecameric recombinant rat SP-D, or the commercially available surfactant preparations Curosurf and Alveofact. Dodecameric rat recombinant SP-D enhanced binding and phagocytosis of the PSG by alveolar macrophages, whereas the recombinant fragment of human SP-D, SP-A, or the surfactant lipid preparations had no effect. In addition, recombinant rat SP-D bound to the surface of the PSG and induced aggregation. Binding, aggregation, and enhancement of phagocytosis by recombinant rat SP-D was completely blocked by EDTA and inhibited by d-maltose and to a lesser extent by d-galactose, indicating the involvement of the carbohydrate recognition domain of SP-D in these functions. The modulation of allergen phagocytosis by SP-D might play an important role in allergen clearance from the lung and thereby modulate the allergic inflammation of asthma.

Allergens↗
PubMedDate not supplied

Soil mixing to decrease surface stratification of phosphorus in manured soils.

Continual applications of fertilizer and manure to permanent grassland or no-till soils can lead to an accumulation of P at the surface, which in turn increases the potential for P loss in overland flow. To investigate the feasibility of redistributing surface stratified P within the soil profile by plowing, Mehlich-3 P rich surface soils (128-961 mg kg(-) in 0-5 cm) were incubated with lower-P subsoil (16-119 mg kg(-1) in 5-20 cm) for 18 manured soils from Oklahoma and Pennsylvania that had received long-term manure applications (60-150 kg P ha(-1) yr(-1) as dairy, poultry, or swine manure for up to 20 yr). After incubating a mixture of 5 g surface soil (0- to 5-cm depth) and 15 g subsoil (5- to 20-cm depth) for 28 d, Mehlich-3 P decreased 66 to 90% as a function of the weighted mean Mehlich-3 P of surface and subsoil (i.e.. 1:3 ratio) (r2 = 0.87). At Klingerstown, Northumberland County, south central Pennsylvania, a P-stratified Berks soil (Typic Dystrochrept) (495 mg kg(-1) Mehlich-3 P in 0- to 5-cm depth) was chisel plowed to about 25 cm and orchardgrass (Dactylis glomerata L.) planted. Once grass was established and erosion minimized (about 20 wk after plowing and planting), total P concentration in overland flow during a 30-min rainfall (6.5 cm h(-1)) was 1.79 mg L(-1) compared with 3.4 mg L(-1) before plowing, with dissolved P reduced from 2.9 to 0.3 mg L(-1). Plowing P-stratified soils has the potential to decrease P loss in overland flow, as long as plowing-induced erosion is minimized.

Agriculture↗
PubMed2006

Effect of manure application timing, crop, and soil type on nitrate leaching.

Timing of manure application affects N leaching. This 3-yr study quantified N losses from liquid manure application on two soils, a Muskellunge clay loam and a Stafford loamy sand, as affected by cropping system and timing of application. Dairy manure was applied at an annual rate of 93 800 L ha(-1) on replicated drained plots under continuous maize (Zea mays L.) in early fall, late fall, early spring, and as a split application in early and late spring. Variable rates of supplemental sidedress N fertilizer were applied as needed. Manure was applied on orchardgrass (Dactylis glomerata L.) in split applications in early fall and late spring, and early and late spring, with supplemental N fertilizer topdressed as NH4NO3 in early spring at 75 kg N ha(-1). Drain water was sampled at least weekly when lines were flowing. Three-year FWM (flow-weighted mean) NO3-N concentrations on loamy sand soil averaged 2.5 times higher (12.7 mg L(-1)) than those on clay loam plots (5.2 mg L(-1)), and those for fall applications on maize-cropped land averaged >10 mg L(-1) on the clay loam and >20 mg L(-1) on the loamy sand. Nitrate-N concentrations among application seasons followed the pattern early fall > late fall > early spring = early + late spring. For grass, average NO3-N concentrations from manure application remained well below 10 mg L(-1). Fall manure applications on maize show high NO3-N leaching risks, especially on sandy soils, and manure applications on grass pose minimal leaching concern.

Agriculture↗
PubMed2005

Ruminal in situ disappearance kinetics of dry matter and fiber in growing steers for common crabgrass forages sampled on seven dates in northern Arkansas.

Southern crabgrass (Digitaria ciliaris [Retz.] Koel.) is often viewed as an undesirable weed, largely because it encroaches upon field and forage crops, gardens, and lawns. However, visual observations of livestock grazing mixed-species pastures suggest that cattle seem to prefer crabgrass to many other summer forages. The objectives of this study were to assess the nutritive value of crabgrass sampled weekly between July 11, and August 22, 2001, and then to determine ruminal in situ disappearance kinetics of DM and NDF for these crabgrass forages. A secondary objective was to compare these kinetic estimates with those of alfalfa (Medicago sativa L.), bermudagrass (Cynodon dactylon [L.] Pers.), and orchardgrass (Dactylis glomerata L.) control hays. All forages were evaluated in situ using five (383 +/- 22.7 kg) ruminally cannulated crossbred (Gelbvieh x Angus x Brangus) steers. Whole-plant crabgrass exhibited more rapid (P < or = 0.002) ruminal disappearance rates of DM (overall range = 0.069 to 0.084 h(-1)) than did bermudagrass (0.054 h(-1)) and orchardgrass (0.060 h(-1)) hays, but disappearance rates were slower (P < 0.001) for crabgrass than for alfalfa hay (0.143 h(-1)). Effective ruminal disappearance of DM was greater (P < 0.001) for crabgrass (overall range = 69.3 to 75.4%) than for all the control hays. Similarly, disappearance rates of NDF for crabgrass (overall range = 0.069 to 0.086 h(-1)) were more rapid (P < 0.001) than observed for bermudagrass and orchardgrass hays; however, NDF in alfalfa disappeared at a faster (P < 0.001) rate (0.107 h(-1)) than crabgrass. These results indicate that crabgrass offers greater effective ruminal degradability of DM and NDF than orchardgrass or alfalfa of moderate quality. More importantly, it potentially offers faster and more extensive ruminal disappearance than perennial warm-season grasses typically found throughout the southeastern United States, and it should likely support improved performance by ruminant livestock in this region.

Animals↗
PubMed2004

Lactation performance of holstein cows fed fescue, orchardgrass, or alfalfa silage.

Perennial grasses are increasingly being used as an integral part of nutrient management plans, but fescue (Festuca arundinacea Schreb.) is often overlooked because of perceived intake problems. A 30-d study was conducted to evaluate the lactation performance of cows fed a fescue silage-based total mixed ration (TMR) compared with orchardgrass (Dactylis glomerata L.) and alfalfa (Medicago sativa L.) silage-based TMR, when forages are harvested at recommended neutral detergent fiber (NDF) levels. Holstein cows (body weight [BW] = 627 +/- 66.0 kg, milk yield = 40.9 +/- 6.93 kg/d, parity = 2.6 +/- 1.44, days in milk = 152 +/- 24.5) were randomly assigned to treatment. Statistical design was a randomized complete block with 10 cows per treatment. The 5 treatments consisted of TMR using first-cutting alfalfa, and first- and second-cutting orchardgrass and tall fescue silage. Diets were formulated to provide 0.95% of BW as forage NDF and contained approximately 18% CP and 1.6 mcal/kg. This resulted in diets of about 30% NDF; for a 612-kg cow, approximately 5.8 kg/d of forage NDF was fed. Second-cutting, grass-based TMR had lower intake than alfalfa and first-cutting forage TMR. Cows consuming second-cutting orchardgrass had lower milk production than did cows consuming other forage TMR. Cows fed fescue TMR had higher milk production than those fed orchardgrass. Indigestible residues were higher, and NDF digestibilities were lower, in second-cutting forages vs. first-cutting forages, likely contributing to the differences observed in intake and resulting differences in milk production. Dairy cows consumed the first-cutting fescue TMR readily and performed as well as those on alfalfa or first-cutting, orchardgrass-based TMR in terms of lactation performance, but fescue and orchardgrass rations will require more concentrate in the ration than alfalfa.

Animal Nutritional Physiological Phenomena↗
PubMed2005

Aerobic stability of wheat and orchardgrass round-bale silages during winter.

Using recently developed technology, balage is often stored in large (1.2 x 1.2 m) round bales that are wrapped in plastic film with an in-line wrapper. The aerobic stability of this fermented forage is important, particularly during winter months when it is fed to livestock or sold as a cash crop. Two types of forage, orchardgrass [Dactylis glomerata L.; 54.4% dry matter (DM)] and wheat (Triticum aestivum L.; 62.4% DM), were packaged in large round bales and wrapped with an in-line wrapper during May 2002. Twenty-one bales of each balage type were unwrapped and exposed to air on Dec. 10, 2002 for 0, 2, 4, 8, 16, 24, or 32 d (ambient temperature range = 0.6 to 19.4 degrees C) to evaluate aerobic stability. For both orchardgrass and wheat balage, final bale weight, concentration of DM, and pH were not affected by exposure time. Across both balage types, DM recoveries were > or = 97% for all bales, indicating that both balage types were very stable when exposed to air. For orchardgrass balage, exposure time had no effect on concentrations of NDF, ADF, hemicellulose, cellulose, or lignin, thereby indicating that little deterioration occurred. Similarly, no contrast relating any fiber component with exposure time was significant for wheat balage. Concentrations of crude protein (CP) were not affected by exposure time for wheat balage, but there was a tendency for exposed orchardgrass bales to have greater concentrations of CP than bales sampled on d 0. Exposure time had no effect on 48-h in situ digestibility of DM for wheat balage, but there was a tendency for a linear increase with exposure time for orchardgrass balage. However, the overall range (78.2 to 80.5%) over the 32-d exposure period was very narrow, and this response is probably of limited biological significance. Generally, concentrations of fermentation acids were low, primarily because of the high concentration of DM within these balages, and only minimal changes in these acids were observed over the exposure interval. These results suggest that the balage evaluated in this trial during winter conditions was very stable after exposure to air for up to 32 d. This should allow for considerable flexibility with respect to feeding, transport, and marketing of balage during winter months without significant aerobic deterioration.

Ammonia↗
PubMed1997

Variability in the pattern of random amplified polymorphic DNA.

The random amplified polymorphic DNA (RAPD) technique is a simple method to detect DNA polymorphism. It is sensitive to reaction conditions. Small changes in the reactants' concentration cause variations in amplification products. Using DNA from Asparagus officinalis, Dactylis glomerata, Mercurialis annua and Escherichia coli, we examined variability in the amplification pattern associated with reaction constituents. An increase in the ratio of Taq DNA polymerase to DNA in the reaction increased the number of amplified fragments. Increasing the concentration of primer resulted in the amplification of low molecular weight DNA fragments, while lowering the concentration resulted in high molecular weight fragments. Subsets of amplified fragments required different concentrations of magnesium for their highest intensity. Mechanical shearing of DNA obtained by sonication led to reduction in amplification of a subset of products. Enzymatic fragmentation of DNA by restriction enzymes led to loss or gain of specific fragments, depending on the DNA, primer, and restriction enzyme. RAPD markers of pooled DNA of anonymous pedigree should be critically evaluated for frequent 'false positive' markers.

Base Composition↗
PubMed2001

Hypothesis: hemimelia and the maintenance of pentadactyly?

The limbs of extant terrestrial vertebrates possess five or fewer digits, yet, polydactyly is accepted as being the ancestral state. Therefore, I propose a hypothesis to account for the maintenance of digital number at five or fewer digits, based on a selective disadvantage associated with polydactylous states in terrestrial vertebrates. This disadvantage is not associated with the polydactyly per se, but rather with the hemimelia which is a common feature of polydactylies in mammals. Hemimelia causes a twisting, or luxation, of the distal segment of the limb, which is due to a malformation of the radius/tibia of the limb. This defect results in the limb being held in an abnormal gait, which causes problems in the locomotion of the animal which would compromise their ability to flourish. Therefore, the abnormal gait and torsion of the limb caused by the hemimelia is acting as a stabilizing force to maintain the dactyly of the tetrapod limb with five or fewer digits.

Animals↗
PubMed1994

Influence of low temperature preincubation on somatic embryogenesis and ethylene emanation from orchardgrass leaves.

The objectives of this study were to determine the effects of low temperature (4 degrees C) preincubation on somatic embryogenesis from orchardgrass (Dactylis glomerata L.) leaf cultures and to relate these effects to ethylene emanation during the preincubation and incubation periods. Experiments were also conducted with an ethylene biosynthesis inhibitor aminooxyacetic acid (AOA). Segments from the innermost two leaves were cultured on SH medium with 30 micromoles dicamba at 4 degrees C for 1 to 7 d before transfer to 21 degrees C. Results from a paired design showed that the embryogenic response of leaf segments preincubated at 4 degrees C was equal or superior to nonpreincubated leaves at all time periods. Ethylene emanation was decreased during the low temperature incubation. Transfer of leaf segments from 4 degrees C to 21 degrees C was accompanied by a burst of ethylene which rose to control levels within 30 min. AOA at 20 and 40 micromoles decreased ethylene emanation but did not stimulate the embryogenic response. We conclude that the stimulation of somatic embryogenesis by low temperature is probably due to factors other than suppression of ethylene biosynthesis.

Aminooxyacetic Acid↗