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  • 1
    ISSN: 1615-6102
    Keywords: Phenylcarbamates ; Multipolar spindles ; Microtubule-organizing centres ; Aneuploidy ; Allium cepa L
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The herbicide carbetamide [(R)-1-(ethylcarbamoyl) ethylphenylcarbamate], in the 0.4 to 0.8 mM range, efficiently induced multipolar mitoses inAllium cepa L. The frequency of multipolar anaphases rose earlier and reached higher values when both concentration and time of treatment increased, up to a maximum of 90% after 1 h of treatment. To identify the physiological target, the kinetics of induction of multipolar mitoses were followed during recovery from very short treatments (5, 10, and 15 min). Tubulin immunodetection showed that phenylcarbamate immediately disrupts the cohesion between the different bundles of microtubule minus ends which converge at the pole. The spindle was rendered multipolar about three times more efficiently in metaphase than in anaphase. The observations do not support any effect of the herbicide on the tubulin polymerization-depolymerization cycle, and suggest that the minus ends of the microtubules remained stabilized in carbetamide. Thus, the density of kinetochore microtubules and their lengths were unmodified in the individual chromosomes which became detached from both spindle poles in response to the herbicide. Extra microtubule-organizing centres for the assembly of both preprophase band and phragmoplast (the tubulin arrays which characterize the microtubular cycle responsible for cytokinesis in plant cells) were also rapidly induced.
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  • 2
    ISSN: 1573-8272
    Keywords: arachidonic acid (AA) ; downstream processing ; eicosapentaenoic acid (EPA) ; polyunsaturated fatty acids ; Porphyridium cruentum ; urea inclusion method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Eicosapentaenoic acid (FPA, 20:5n-3) and arachidonic acid (AA, 20:4n-3)were obtained from the microalga Porphyridium cruentum by a three-stepprocess: fatty acid extraction by direct saponification of biomass,polyunsaturated fatty acid (PUFA) concentration by urea inclusion complexingand EPA isolation by high-performance liquid chromatography (HPLC). Twosolvents were tested for direct saponification of lipids in biomass. Themost efficient solvent, ethanol (96% v/v), extracted 75% ofthe fatty acids. PUFAs concentration by urea inclusion employed a urea/fattyacid ratio of 4:1 wt/wt at the crystallization temperatures of 4°C and28°C. Concentration factors were similar at both temperatures, but theEPA and AA recoveries were higher at 28°C (67.7% and 61.8%for the two acids, respectively). EPA and AA were purified from this PUFAconcentrate using analytical scale HPLC and the best results of thisseparation were scaled up to preparative level (4.7 i. d. × 30 cmcompression radial cartridge). A 94.3% pure EPA fraction and a81.4% pure AA fraction were obtained. Suitability of severalmicroalgae (Porphyridium cruentum, Phaeodactylum tricornutum and Isochrysisgalbana) and cod liver oil as sources of highly pure PUFAs, mainly EPA, wascompared.
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  • 3
    ISSN: 1573-5176
    Keywords: eicosapentaenoic acid (EPA) ; Phaeodactylum tricornutum ; downstream processing ; wet biomass ; gram-scale HPLC purification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Eicosapentaenoic acid (EPA, 20:5n-3) was obtained from the microalgaPhaeodactylum tricornutum following a three-step process: fatty acid extraction by direct saponification of wet biomass, polyunsaturated fatty acid (PUFA) concentration by formation of urea inclusion compounds and EPA isolation by preparative HPLC. Direct saponification of wet biomass was carried out with KOH-ethanol (96% v:v) (1 h, 60 °C), extracting 91% of the EPA. PUFAs were concentrated by the urea method with an urea/fatty acid ratio of 4:1 at a crystallization temperature of 28 °C using methanol as the urea solvent. An EPA concentration ratio of 1.5 (55.2/36.3) and recovery of 79% were obtained. This PUFA concentrate was used to obtain 95.8% pure EPA by preparative HPLC, using a reverse-phase column (C18, 4.7 cm i.d. × 30 cm) and methanol-water (1% AcH) 80:20 w/w as the mobile phase. Ninety-seven per cent of EPA loaded was recovered and 70% EPA present in theP. tricornutum biomass was recovered in a highly pure form by means of this three-step downstream processing. In each of the HPLC preparative runs, 635 mg PUFA concentrate were loaded, obtaining 326 mg of a highly concentrated EPA fraction (2.46 g d−1). Finally, a preliminary cost statement has been calculated.
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  • 4
    ISSN: 1615-6102
    Keywords: Carbamates ; Microtubules ; Mitosis ; Cytokinesis ; Caffeine ; Allium cepa L
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Indirect immunodetection of tubulin showed that the herbicide carbetamide activated silent signals left by the preprophase band (PPB) and by old phragmoplasts. Thus, after half an hour of treatment, 5.3% of anaphases inAllium cepa L. meristems showed spindle microtubules pointing to sites of the longitudinal cell membranes which, under control conditions, would only start attracting microtubules from the growing phragmoplast at late telophase. After 2 h, 12.8% of the telophases showed not only the expected phragmoplast between the two sister nuclei, but one or two additional phragmoplasts, at one or both cell tips, the sites of the phragmoplasts from the telophases of previous cycles. A few binucleate cells, obtained by aborting phragmoplast formation by a short caffeine treatment, developed three phragmoplasts in their next mitosis (bimitosis) in the presence of carbetamide: one between each sister pair of telophasic nuclei plus an extra one. The latter also occupied the site of the phragmoplast of the telophase of the previous cycle.
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  • 5
    ISSN: 1432-2048
    Keywords: Keywords: Actin ; Allium ; Mitotic spindle ; Phragmoplast ; Preprophase ; Tubulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The present work establishes a correlation between cell length and patterns of mitotic microtubular assemblies in Allium cepa L. root meristems. Binucleate cells were formed by a short caffeine treatment which aborted the formation of the phragmoplast during telophase. The largest binucleate cells (about 50 μm in length) behaved as two contiguous mononucleate cells in their next mitosis: they developed two preprophase bands (PPBs), one around each nucleus, where two spindles and two phragmoplasts were subsequently formed. On the other hand, the shortest binucleate cells (about 36 μm in length) formed a single PPB at the site of the aborted phragmoplast and, in the medium-sized cells (about 44 μm) in which the single PPB formed around the nucleus possessing the largest cytoplasmic environment, the two mitotic spindles and the new phragmoplasts moved to, or were assembled in the position of the phragmoplast that had been aborted one cycle earlier. Some rules derive from these observations. First of all, the aborted phragmoplast left a signal for microtubule positioning which was still operative one cycle later, in two-thirds of the bimitoses. Also, that formation of the PPB is dispensable. Moreover, its development does not always predict the future division plane, because of the presence of competing old signals which are stronger than those shed by the PPB in the same mitosis, but which fade away with distance. Finally, the positional signals were reinforced when the ratio of monomeric to fibrillar actin was increased by cytochalasin D during their shedding. When this drug was given simultaneously with caffeine, the frequency of bimitoses which, one cycle later, developed spindles and phragmoplasts in the positions of the old phragmoplast increased. On the other hand, those frequencies dropped in relation to control when the cytochalasin D treatment took place during bimitosis, indicating that at this time the treatment reinforced the signals produced in bimitosis itself.
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  • 6
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Roots from Allium cepa L. (cv. Francesa) bulbs in which a maximum of two nucleoli per nucleus developed were selected for this study. Five rDNA clusters were detected by fluorescent in situ hybridization on chromosomal squashes (2n = 16) with a rhodamine-labelled wheat rDNA repeat. The rDNA clusters were located on four chromosomes: the largest cluster occurred on the small arm of a single homologue of the smallest pair 8. Its homologue showed two different small rDNA clusters, one near each telomere. The two homologues of the satellited chromosomes 6 also showed different rDNA contents, which were intermediate to those found in pair 8. The same five well-differentiated hybridization signals were observed in interphase cells that were inactive in transcription because they were in dormant roots, or in proliferating ones in which the synthesis of the large rRNA precursor was prevented. After multipolarizing agent was applied in anaphase followed by inhibition of cytokinesis, multinucleate autotetraploid cells were formed, which often contained more than four nucleoli. Thus, at least two of the three nucleolar organizer regions that consistently failed to develop a nucleolus in normal mononucleate cells were capable of developing nucleoli when segregated into different nuclei in multinucleate cells.
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  • 7
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Sister chromatid cores, kinetochores and the connecting strand between sister kinetochores were differentially silver stained to analyse the behaviour of these structures during meiosis in normal and two spontaneous desynaptic individuals of Chorthippus jucundus (Orthoptera). In these desynaptic individuals most of the chromosomes appear as univalents and orient equationally in the first meiotic division. Despite this abnormal segregation pattern, the changes in chromosome structure follow the same timing as in normal individuals and seem to be strictly phase dependent. Chromosomes in the first prometaphase have associated sister kinetochores and sister chromatid cores that lie in the chromosome midline; we propose that this promotes the initial monopolar orientation of chromosomes. However, the requirements of tension for stable attachment to the spindle force the autosomal univalents to acquire amphitelic orientation. Sister kinetochores behave in a chromosome orientation-dependent manner and, in the first metaphase, they appear to be interconnected by a strand that can be detected by silver impregnation, as seen in the second metaphase of wild-type individuals. The disappearance of the sister kinetochore-connecting strand, needed for equational chromatid segregation, however, can only take place in the second meiotic division. This connecting strand is ultimately responsible for the inability of chromosomes to segregate sister chromatids in the first anaphase.
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  • 8
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. When DNA topoisomerase II (topo II) activity is inhibited with a non-DNA-damaging topo II inhibitor (ICRF-193), mammalian cells become checkpoint arrested in G2-phase. In this study, we analyzed chromosome structure in cells that bypassed this checkpoint. We observed a novel type of chromosome aberration, which we call Ω-figures. These are entangled chromosome regions that indicate the persistence of catenations between nonhomologous sequences. The number of Ω- figures per cell increased sharply as cells evaded the transient block imposed by the topo II-dependent checkpoint, and the presence of caffeine (a checkpoint-evading agent) potentiated this increase. Thus, the removal of nonreplicative catenations, a process that promotes chromosome individualization in G2, may be monitored by the topo II-dependent checkpoint in mammals.
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    ISSN: 1476-4431
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The Rescue Glide Sked provides a practical means of moving a recumbent, non-ambulatory or injured horse from the site of an accident. Horses with serious injuries, displaying severe malnutrition or neurological symptoms, can be easily moved out of a stall or even down a trail to a horse ambulance for transport to a veterinary facility. It is a specialty cut piece of 8′× 4′ recycled polypropylene with tie-down straps and steel attachment points for winch loading into an equine ambulance. A horse must be fully sedated during transport on the rescue glide to prevent further injury to itself or rescuers. Moving a recumbent horse is very difficult due to the weight of the animal, often causing damage to the head and eyes, and with many safety concerns for the rescuers (struggling, kicking). It may take 8 to 10 people to move a horse just a few feet, especially uphill or on high friction surfaces. Benefits of the Rescue Glide include that the plastic reduces the friction of the weight of the animal on the ground surface, so fewer people are needed to move the animal. The tough resilient plastic is flexible so it goes easily over obstacles such as logs, roots, or through ditches. It folds up around the animal's body to get through a standard stall door or tight spaces as might be encountered on a trail. The Glide may be attached to a winch, ropes pulled by human rescuers, or even vehicle (ATV, car, etc.)The practical use of the Rescue Glide has been demonstrated in numerous situations including severe limb injuries, neurological compromise, geriatric, recumbent/unable to rise, severe neglect/malnutrition, and recovery/removal of dead large animals. The equipment has been used at race tracks and riding competition events for transport of animals into ambulances, as well as by veterinary rescue response teams in trail riding accidents, pasture accidents, and severe trailer injuries.The Rescue Glide, in conjunction with an equine ambulance trailer, provides a safe and suitable means of transport of large animals to veterinary facilities and should be a part of the equine practitioner's emergency equipment.
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  • 10
    ISSN: 1476-4431
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Improved options for the successful transport of horses trapped in inaccessible areas (floodwater, steep ravines, etc.) during a disaster or emergency are available to practitioners using helicopter assets and the Anderson Sling™. Horses present a particularly difficult problem to remove from the rescue environment of a wide flooded area, or difficult steep terrain far from access by vehicles or heavy equipment. Due to their fractious and fearful nature, they may fight any effort to walk, climb or swim them to safety, and those attempts are inherently very dangerous for the rescuer(s). Unfortunately, many disaster or emergency scenarios may occur in areas not conducive to the use of other options (barge, rescue glide, simple vertical lift sling). Veterinary practitioners on scene should have familiarity with helicopter sling-load operations.The use of cargo nets, inappropriate home-made slings, and inadequate equipment has contributed to disastrous efforts by well-intentioned rescuers. There have even been desperate attempts at sling loading of cattle by roping the horns or one leg and transporting them into a waiting truck for removal from public lands.The Anderson Sling™ has been successfully used for helicopter operations in multiple emergencies and training demonstration flights, and is the only Equine Sling recommended for this purpose. Although it was originally intended for clinical use in long-term recovery cases, it has become the industry standard for helicopter operations with equines because of its demonstrated safety margin, design and strength. In clinical use, leg straps further distribute the animal's weight to the legs, but are not necessary in rescue lifts. In some states, there are Large Animal Rescue Teams associated with the Veterinary School, the State Emergency Management Association, or local private Equine Ambulance Services that may have equipment and personnel trained in helicopter sling-loading. This is a specialty interest that requires prior coordination, significant planning, and training of all personnel involved.
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