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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: 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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  • 3
    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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  • 4
    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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  • 5
    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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  • 6
    ISSN: 1600-0536
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Fragrances contain several hundreds of different chemicals, a few major and many minor, which are responsible for the complexity of the odour. Fragrances are a major cause of allergic contact dermatitis. As a diagnostic tool, the current fragrance mix is very useful though not ideal. A 50-year-old woman presented with a pruriginous, erythematous eruption, characterized by papules, vesicles, exudation and crusting over the neck and chest. With the suspicion of fragrance allergy, patch testing was performed. Initially, the only positive reaction observed was with her own eau de toilette named Woman®. The TRUE Test® fragrance mix patch test was negative. Chemical fractionation of Woman® perfume concentrate was combined with a sequenced patch testing procedure and with structure-activity relationship studies. Ingredients supplied by the manufacturer were also included in the study. Benzophenone-2, Lyral®, α-hexyl cinnamic aldehyde and α-damascone were found to be responsible for the patient's contact allergy to the commercial product. These substances contain chemical structural alerts giving them antigenic ability. The common use of new chemicals to manufacture fragrances, and the increased number of patients sensitive to them but with negative fragrance mix reactions, makes it necessary to identify new potential fragrance sensitizers in commercial products.
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  • 7
    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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  • 8
    ISSN: 1365-4632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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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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