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  • Bemisia tabaci  (5)
  • Motor control  (5)
  • Bemisia argentifolii  (3)
  • Muscle contraction  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Variation in biological characteristics and esterase patterns among populations of Bemisia tabaci, and the association of one population with silverleaf symptom induction (1991)
    Springer
    Entomologia experimentalis et applicata 61 (1991), S. 211-219 
    Details
    ISSN: 1570-7458
    Keywords: Insecta ; Bemisia tabaci ; whitefly ; oviposition ; survival ; squash silverleaf
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Biological characteristics (oviposition and survival rates) and esterase banding patterns in native PAGE were investigated to evaluate variation among three populations of Bemisia tabaci Gennadius (Homoptera: Aleyrodidae). Reproductive capabilities of whiteflies from cotton (Gossypium hirsutum L.) and pumpkin (Cucurbita maxima Duchesne) populations were similar on the three host plant species tested. These populations, which had the same wild-type field origin, reproduced better on either cotton and pumpkin than on poinsettia (Euphorbia pulcherrima Willdenow). In contrast, poinsettia whiteflies exhibited relatively similar reproductive capabilities for the three host species tested. Pumpkin and cotton whiteflies had similar esterase banding patterns (‘A’ type), while poinsettia whiteflies yielded a different banding pattern (‘B’ type). In transmission studies, whiteflies from cotton or pumpkin sources did not induce silverleaf (SSL) or white stem (WS) symptoms in Cucurbita spp. tested. In contrast, poinsettia whiteflies were associated routinely with SSL and WS symptoms in Cucurbita spp. following colonization by whitefly adults. From these data, it was possible to correlate a specific esterase banding pattern (A or B) with reproductive capabilities and the ability to induce SSL and WS symptoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00187724
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  • 2
    Electronic Resource
    Electronic Resource
    Characterization and distribution of esterase electromorphs in the whitefly,Bemisia tabaci (Genn.) (Homoptera: Aleyrodidae) (1995)
    Springer
    Biochemical genetics 33 (1995), S. 205-214 
    Details
    ISSN: 1573-4927
    Keywords: Bemisia tabaci ; Bemisia argentifolii ; cotton whitefly ; squash silverleaf disorder ; sweetpotato whitefly ; tobacco whitefly ; virus vector
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Esterase profiles were examined for over 40 populations of the whitefly,Bemisia tabaci, obtained from native and cultivated plant hosts worldwide. Twelve unique electromorphs were identified from distinct populations concentrated largely in Central America, Africa, and India. One electromorph, type B, has recently been proposed as a separate species,Bemisia argentifolii, and has recently spread throughout much of the world. When considered with evidence from mating studies and the ability to induce phytotoxic disorders (squash silverleaf disorder), our data suggest that the single taxonBemisia tabaci may actually represent a species complex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00553619
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  • 3
    Electronic Resource
    Electronic Resource
    Characterization and distribution of esterase electromorphs in the whitefly,Bemisia tabaci (Genn.) (Homoptera: Aleyrodidae) (1995)
    Springer
    Biochemical genetics 33 (1995), S. 205-214 
    Details
    ISSN: 1573-4927
    Keywords: Bemisia tabaci ; Bemisia argentifolii ; cotton whitefly ; squash silverleaf disorder ; sweetpotato whitefly ; tobacco whitefly ; virus vector
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Esterase profiles were examined for over 40 populations of the whitefly,Bemisia tabaci, obtained from native and cultivated plant hosts worldwide. Twelve unique electromorphs were identified from distinct populations concentrated largely in Central America, Africa, and India. One electromorph, type B, has recently been proposed as a separate species,Bemisia argentifolii, and has recently spread throughout much of the world. When considered with evidence from mating studies and the ability to induce phytotoxic disorders (squash silverleaf disorder), our data suggest that the single taxonBemisia tabaci may actually represent a species complex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02401851
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  • 4
    Electronic Resource
    Electronic Resource
    Morphological variation inBemisia endosymbionts (1995)
    Springer
    Protoplasma 189 (1995), S. 194-202 
    Details
    ISSN: 1615-6102
    Keywords: Bacteria ; Bemisia tabaci ; Bemisia argentifolii ; Endosymbionts ; Microorganism ; Symbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ultrastructure of the endosymbionts of several populations of whitefly (Homoptera: Aleyrodidae) was examined using transmission electron microscopy. Consistent differences in morphology and relative number of endosymbionts were observed between species and biotypes of whitefly within the Bemisia taxon.Bemisia argentifolii (=B. tabaci B biotype) individuals from Hawaii, Florida, and Arizona contained two morphological types of microorganisms housed within the mycetocyte cells of immature whiteflies. In contrast, individuals from populations ofB. tabaci A biotype from Arizona and Mexico, andB. tabaci Jatropha biotype from Puerto Rico, consistently contained three distinct morphological types of microorganisms within their mycetocytes. Organisms fromB. tabaci A and Jatropha biotypes differed from each other in the relative frequency of each type of microorganism. These observations suggest that different whitefly biotypes may have variable combinations of micro-fauna, with some possibly unique to each group, and furthers the hypothesis that variation in whitefly endosymbionts may be associated with the development of biotypes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01280174
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  • 5
    Electronic Resource
    Electronic Resource
    Influence of muscle activation dynamics on reaction time in the elderly (1994)
    Springer
    European journal of applied physiology 69 (1994), S. 344-349 
    Details
    ISSN: 1439-6327
    Keywords: Aging ; Electromyography ; Reaction time ; Motor control ; Muscle contraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aim of this investigation was to determine whether age-related changes in the dynamics of muscle activation were, in part, responsible for longer reaction times (RT) in the elderly. A group of 12 young (mean age, 20.6 years) and 12 elderly (mean age, 64.3 years) women performed a series of ballistic forearm supination movements in response to an auditory stimulus while using a simple reaction time test. Surface electromyographic waveforms from biceps brachii (agonist) and pronator teres (antagonist) muscles were recorded, together with the angle-time curves representing the motion of the forearm, on to an IBM compatible microcomputer. The results showed that an age-related increase (P〈0.05) in motor reaction time (MRT) contributed to longer RT in the elderly. In addition, the longer (P〈0.05) MRTs in the elderly were associated with a significantly slower rate (P〈0.05) of biceps brachii muscle activation and a significantly increased proportion (P〈0.05) of the initial biceps brachii muscle burst required to initiate the movement. This data suggested that an important part of the slowing of motor behaviour, commonly observed with increasing age, may be due to either decreases in the ability of aged skeletal muscle to rapidly generate tension or to a reduction in motor drive.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392041
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  • 6
    Electronic Resource
    Electronic Resource
    Muscles within muscles: the neuromotor control of intra-muscular segments (1998)
    Springer
    European journal of applied physiology 78 (1998), S. 219-225 
    Details
    ISSN: 1439-6327
    Keywords: Key words Functional differentiation ; Electromyography ; Deltoid ; Motor control ; Muscle function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aim of this investigation was to anatomically identify, and then determine the function of, individual segments within the human deltoid muscle. The anatomical structure of the deltoid was determined through dissection and/or observation of the shoulder girdles of 11 male cadavers (aged 65–84 years). These results indicate that the deltoid consists of seven anatomical segments (D1–D7) based upon the distinctive arrangement of each segment's origin and insertion. Radiographic analysis of a cadaveric shoulder joint suggested that only the postero-medial segment D7 has a line of action directed below the shoulder joint's axis of rotation. The functional role of each individual segment was then determined utilising an electromyographic (EMG) technique. Seven miniature (1 mm active plate; 7 mm interelectrode distance) bipolar surface electrodes were positioned over the proximal portion of each segment's muscle belly in 18 male and female subjects (18–30 years). EMG waveforms were then recorded during the production of rapid isometric shoulder abduction and adduction force impulses with the shoulder joint in 40 degrees of abduction in the plane of the scapula. Each subject randomly performed 15 abduction and 15 adduction isometric force impulses following a short familiarisation period. All subjects received visual feed back on the duration and amplitude of each isometric force impulse produced via a visual force-time display which compared subject performance to a criterion force-time curve. Movement time was 400 ms (time-to-peak isometric force) at an intensity level of 50% maximal voluntary contraction. Temporal and intensity analyses of the EMG waveforms, as well as temporal analysis of the isometric force impulses, revealed the neuromotor control strategies utilised by the CNS to control the activity of each muscle segment. The results showed that segmental neuromotor control strategies differ across the breadth of the muscle and that individual segments of the deltoid can be identified as having either “prime mover”, “synergist”, “stabiliser” or “antagonist” functions; functional classifications normally associated with whole muscle function. Therefore, it was concluded that the CNS can “fine tune” the activity of at least six discrete segments within the human deltoid muscle to efficiently meet the demands of the imposed motor task.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004210050410
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  • 7
    Electronic Resource
    Electronic Resource
    Transition from slow to ballistic movement: development of triphasic electromyogram patterns (1991)
    Springer
    European journal of applied physiology 63 (1991), S. 381-386 
    Details
    ISSN: 1439-6327
    Keywords: Motor control ; Electromyography ; Motor skill ; Triphasic electromyogram ; Muscle contraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The purpose of this investigation was to determine how the triphasic electromyogram (EMG) pattern of muscle activation developed from the agonist muscle only pattern as movement time (t mov) decreased. Six adult women produced a series of 30° elbow extension movements in the horizontal plane at speeds ranging from ballistic (〈 400-ms t mov) to very slow (〉 800-ms t mov). Surface EMG from triceps brachii (agonist) and biceps brachii (antagonist) muscles were recorded, together with elbow angle, on a microcomputer. The results showed that triphasic EMG patterns developed systematically as t mov decreased from 1000 ms to 〈 200 ms. In trials with very long t mov, many elbow extension movements were produced by a single continuous activation of the agonist triceps brachii muscle. As t mov decreased however, agonist activation became predominantly burst-like and other components of the triphasic EMG pattern [activation of the antagonist (Ant) and second agonist activation (Ag2)] began to appear. At the fastest movement speeds, triphasic EMG patterns (Ag1-Ant-Ag2, Ag1 being first activation of agonist muscle) were always present. This data indicated that the triphasic pattern of muscle activation was not switched on when a particular t mov was achieved. Rather, each component systematically developed until all were present, as distinctive bursts of activity, in most trials with t mov less than 400 ms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00364466
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  • 8
    Electronic Resource
    Electronic Resource
    The electromyographical basis of inaccurate motor performance (1988)
    Springer
    European journal of applied physiology 58 (1988), S. 132-140 
    Details
    ISSN: 1439-6327
    Keywords: Motor control ; Motor skill ; Electromyography ; Inaccuracy ; Isometric
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The aim of this study was to investigate the electromyographical basis of inaccurate movement by identifying the variate and invariate characteristics of a ballistic, isometric precision-grip skill. Our results have shown that in most subjects investigated, IEMG, discharge rate and the paterns of muscle synergy were variate movement parameters while the sequence of muscle activation, the relative duration of muscle activity and the time to peak force (rise-time) remained essentially invariante. Based on these results, we can conclude that inaccurate performance of this skill, in most of the subjects investigated, was more dependant upon changes in muscle IEMG than in alterations in the temporal sequencing of muscle activity. It was apparent that from trial to trial, subjects had more difficulty in reproducing the appropriate levels of muscle contraction and synergy than in reproducing the required periods of action.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00636616
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  • 9
    Electronic Resource
    Electronic Resource
    Electromyographic basis of inaccurate movement; its dependence upon the mode of muscle contraction (1991)
    Springer
    European journal of applied physiology 62 (1991), S. 162-170 
    Details
    ISSN: 1439-6327
    Keywords: Motor control ; Electromyography ; Muscle contraction ; Inaccurate movement ; Motor skill
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The electromyographic basis of inaccurate performance was investigated in two rapid precision-grip skills controlled by concentric and eccentric muscle contractions respectively. Surface electromyograms, recorded from the first dorsal interosseous (DI), adductor pollicis (AP) and abductor pollicis brevis, were utilised to identify changes in the timing and intensity of muscle activation which may be responsible for inaccurate performance. The results showed that when fast precision-grip skills were controlled by concentric DI and AP muscle contractions, variations in the intensity of muscle contraction were responsible for inaccurate performance. However, when these skills were controlled by eccentric DI and AP muscle contractions, inaccurate performance resulted from variations in the timing of muscle activation. It was concluded that the nature of the deficiency in the patterns of muscle activation resulting in inaccurate performance was dependent upon the type of muscle contraction used in the skill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00643736
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  • 10
    Electronic Resource
    Electronic Resource
    The status ofBemisia tabaci (Hom.: Aleyrodidae),Trialeurodes vaporariorum (Hom.: Aleyrodidae) and their natural enemies in Crete (1993)
    Springer
    BioControl 38 (1993), S. 405-410 
    Details
    ISSN: 1573-8248
    Keywords: Bemisia tabaci ; Crete ; natural enemies ; Trialeurodes vaporariorum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Résumé Bemisia tabaci (Gennadius) a été signalé pour la première fois en Crète en 1992. L'aleurode est confiné au sud-est de l'île.Trialeurodes vaporariorum (Westwood) est l'aleurode prédominant au nord et à l'ouest de l'île. Trois prospections pour les ennemis naturels deB. tabaci ont été faites en Crète en 1992 et 1993. Ces prospections ont eu pour résultat la collecte de 4 espèces d'Encarsia, unEretmocerus sp. et un champignon pathogène,Paecilomyces farinosus (Holm Ex X. F. Gray) Brown & Smith.B. tabaci etT. vaporariorum ont été trouvés sur les cultures maraîchères, plantes ornementales et mauvaises herbes. Partout dans l'île, les populations des deux espèces ont été sévèrement réduites sur les plantes hôtes à l'extérieur pendant l'hiver 1992/93. Les contraintes climatiques, la concurrence avecT. vaporariorum pour les niches, et des ennemis naturels efficaces, peuvent expliquer la dispersion limitée deB. tabaci en Crète.
    Notes: Abstract The non «B» biotype ofBemisia tabaci (Gennadius) is recorded for the first time in Crete in 1992, in the north east and south east of the island.Trialeurodes vaporariorum (Westwood) is the predominant whitefly on plants in the north and west of the island. Three surveys of Crete were made in 1992 and 1993 for natural enemies ofB. tabaci andT. vaporariorum and resulted in the collection of 4 species ofEncarsia, (plus a number of species that are unidentifiable at this time), anEretmocerus sp. (unidentifiable at this time) and a fungal pathogen,Paecilomyces farinosus (Dickson Ex Fries) Brown & Smith.Encarsia adrianae was identified fromT. vaporariorum; which constitutes its most westerly distribution point and a new host record respectively.B. tabaci andT. vaporariorum were found on horticultural crops, ornamentals and weeds. Populations of both whitefly species were severely depleted on field hosts throughout the island during the winter of 1992/93. Climatic constraints, competition withT. vaporariorum in otherwise suitable niches, effective natural enemies and an observed low level of polyphagy may explain the present limited distribution of the non «B» biotype ofB. tabaci in Crete.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02374458
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