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  • 1
    ISSN: 1432-1106
    Keywords: Key words Long-latency reflexes ; Magnetic brain stimulation ; Sensory feedback
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Stimulation of cutaneous foot afferents has been shown to evoke a facilitation of the tibialis anterior (TA) EMG-activity at a latency of 70–95 ms in the early and middle swing phase of human walking. The present study investigated the underlying mechanism for this facilitation. In those subjects in whom it was possible to elicit a reflex during tonic dorsiflexion while seated (6 out of 17 tested), the facilitation in the TA EMG evoked by stimulation of the sural nerve (3 shocks, 3-ms interval, 2.0–2.5× perception threshold) was found to have the same latency in the swing phase of walking. The facilitation observed during tonic dorsiflexion has been suggested to be – at least partly – mediated by a transcortical pathway. To investigate whether a similar mechanism contributes to the facilitation observed during walking, magnetic stimulation of the motor cortex (1.2× motor threshold) was applied in the early swing phase at different intervals in relation to the cutaneous stimulation in 17 subjects. In 13 of the subjects, the motor potentials evoked by the magnetic stimulation (MEPs) were more facilitated by prior sural-nerve stimulation (conditioning-test intervals of 50–80 ms) than the algebraic sum of the control MEP and the cutaneous facilitation in the EMG when evoked separately. In four of these subjects, a tibialis anterior H-reflex could also be evoked during walking. In none of the subjects was an increase of the H-reflex similar to that for the MEP observed. In five experiments on four subjects, MEPs evoked by magnetic and electrical cortical stimulation were compared. In four of these experiments, only the magnetically induced MEPs were facilitated by prior stimulation of the sural nerve. We suggest that a transcortical pathway may also contribute to late cutaneous reflexes during walking.
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  • 2
    ISSN: 1432-1106
    Keywords: Key words H-reflex ; Motor units ; Motor evoked potentials ; Motoneuron recruitment ; Transcranial magnetic stimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The responses of 34 extensor-carpi-radialis motor units to graded transcranial magnetic stimulation (TMS) and electrical stimulation of the radial nerve were investigated in six human subjects. Simultaneously with the recording of the single motor-unit discharges, motor-evoked potentials (MEPs) and H-reflexes evoked by the two types of stimulation were recorded by surface electrodes and expressed as a percentage of the maximal motor response (Mmax). Ten motor units were activated in the H-reflex when it was less than 5% of Mmax, but not in the MEP even when it was 15% of Mmax. The opposite was observed for three motor units. Eleven motor units were recruited by both stimuli, but with significantly different recruitment thresholds. Only ten motor units had a threshold similar to TMS and radial nerve stimulation. From these observations, we suggest that caution should be taken when making conclusions regarding motor cortical excitability based on changes in the size of MEPs, even when it is ensured that there are no similar changes in background EMG-activity or H-reflexes.
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  • 3
    ISSN: 1433-3023
    Keywords: Bladder ; Continence ; Levator ani ; Physiotherapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The dynamic anatomical response of the normal pelvic floor to voluntary pelvic floor contractions was documented using magnetic resonance imaging. Sequences of coronal, sagittal and transverse images in the relaxed and the contracted state were obtained from 17 young, asymptomatic volunteers trained to perform pelvic floor exercises correctly. The images were processed digitally and computer colored to indicate dynamic changes produced as a result of contractions. Gross transverse sections through a human female cadaver were photographed and digitized to provide a reference of pelvic anatomy. A 3D rendition of the processed MR images was made to illustrate the extent of pelvic floor contraction. The results illustrate the changes produced by voluntary pelvic floor contractions in all planes scanned. Quantitative measurements of selective structures around the bladder were made to show the magnitude of pelvic floor displacement during contraction. The dynamic imaging illustrates the extent of changes in the normal pelvic floor that are produced by pelvic floor exercises and give a measure of the displacement of the bladder and the levator ani.
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  • 4
    ISSN: 1365-2842
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Albeit never substantiated through experimental and clinical evidence, the theoretical linchpin of the mechanics of a so-called whiplash injury of the temporomandibular joint (TMJ) is the postulate that a pre-existing depressor force (continual anchoring force), generated by the anterior suprahyoid (SH) muscles, will always act on the mandible and cause traumatic mouth opening (anterior acceleration of the TMJ condyles) when the neck is extended (posterior acceleration of the head). To test aspects of this postulate, six subjects assumed the positions of neutral (0°), medium (32°) and maximum (58°) neck extension while the mandible was in its postural positions of rest and light centric occlusion. By means of surface electromyography, it was shown that the relative contractile activities of the anterior SH muscles never exceeded 7·3% of the contractile activity required to anchor the mandible in a position of maximum depression. By means of electrognathography, it was shown that the maxillary and mandibular incisors were never separated by more than 2·6 mm during neutral, medium, and maximum extension of the neck. In other words, during neck extensions there was no evidence of a continual or induced voluntary or involuntary depressor force that would and could anchor the mandible in a position of traumatic mouth opening. Accordingly, and in agreement with other biophysical and biomedical evidence, it was concluded that there is no foundation for the pseudoscientific speculations and unsubstantiated opinions offered in support of a concept and diagnosis of a so-called TMJ whiplash injury. Additionally, this study found co-activation of cervical flexor muscles and mandibular elevator as well as depressor muscles.
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  • 5
    ISSN: 1420-908X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
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  • 6
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Saccharomyces cerevisiae was inoculated into a yeast nitrogen base with either glycerol or glucose as carbon source. Cell proliferation was followed by colony counts on agar medium. Cells in the glycerol-supplemented medium divided less than once in 10 days. When glucose, 6-deoxy-glucose or protoporphyrin IX was added, the cells had doubling times of about 24 h and increased in number to about 0.5 × 106 cells ml−1 Addition of either of the protein kinase C activators oleoyl-acetylglycerol or phorbol-12-myristate-13-acetate did not activate cell proliferation in the glycerol medium. However, when (i) glucose was combined with either protoporphyrin IX or chlorophyllin, or (ii) either protoporphyrin IX or chlorophyllin was combined with either of the protein kinase C activators, the cells had doubling times of about 12 h. Hence, (i) glucose can act as both a carbon source and a signalling molecule for proliferation, and (ii) two systems are involved in activating cell proliferation in S. cerevisiae: one operating through a protein kinase C system and another through a guanylate cyclase system.
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  • 7
    ISSN: 1600-0560
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Angiogenesis and the extracellular matrix are fundamental to tumor progression from in situ to invasive and metastatic disease. Laminin, a major glycoprotein integrated into basement membranes, is observed in angiogenesis and tumorigenesis. A recent study described an association between melanoma cells and endothelial cells via an amorphous matrix containing laminin. In the current study, we have examined 45 cases of human primary and metastatic melanomas by electron microscopy for the presence of an amorphous matrix. We observed an amorphous matrix without a clearly delineated lamina or basement membrane in 41 of the 45 melanomas studied. 28 cases with tissue blocks available for study were examinated by immunohistochemistry for the expression of laminin and type IV collagen. We observed die presence of an angiocentric matrix containing laminin in 24 of the 28 melanomas studied. Since laminin is involved in tumor migration, the presence of laminin between melanoma cells and small vessels suggests a role for this material in periendothelial tumor migration. However, further study is required to characterize the nature of this material and the mechanisms involved.
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  • 8
    ISSN: 1365-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: CD73 is a bifunctional glycosyl phosphatidylinositol anchored leucocyte differentiation antigen which has specific ecto-5′-nucleotidase (ecto-5′-NT) activity and is an accessory T-lymphocyte activation molecule. The aim of the present study was to investigate the CD73 expression on blood mononuclear cells (BMC) from a group of patients with primary immunoglobulin deficiency (IGD). This group of patients had both significantly decreased levels of ecto-5′-NT on BMC (P = 0.002) and decreased numbers of CD73 molecules per CD73+ lymphocyte (P = 0.01). Five of the 10 patients had a decreased percentage of CD73+ lymphocytes. Among B-lymphocytes the patients had normal percentages of CD73+ cells but four of the 10 patients had numbers of CD73 molecules per CD73+ B-lymphocyte below the normal range. Among CD4-lymphocytes three out of 10 patients had percentages of CD73+ below the normal range and four out of 10 patients had decreased percentages of CD73+ CD8-lymphocytes. Significant correlations were found between in vitro proliferative responses to mitogens and the number of CD73 molecules per CD73+ lymphocyte (rs = 0.60, P 〈 0.01) and per CD73+ CD8-lymphocyte (rs = 0.64, P 〈 0.02). In addition, a positive correlation was found between ability to proliferate and level of ecto-5′-NT on BMC (rs = 0.53, P 〈 0.05). Furthermore the ability of BMC to synthesize ecto-5′-NT was studied. During 2 days' culture ecto-5′-NT activity increased markedly on BMC from both patients and healthy donors. The level of activity on BMC from all patients attained levels higher than on freshly isolated BMC from healthy donors. This shows that the decreased levels of ecto-5′-NT found on freshly isolated BMC from patients with IGD is due to defective regulation of the enzyme activity in vivo
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  • 9
    ISSN: 1365-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The authors tested an alternative method for CD4 and CD8 T lymphocytes enumeration, the immunoalkaline phosphatase method (IA), in three African countries and in Denmark. The IA determinations from 136 HIV antibody positive and 105 HIV antibody negative individuals were compared to the corresponding results obtained by flow cytometry (FC) performed in the respective countries. The authors found good correspondence between the two methods for measurements of CD4 and CD8 T lymphocytes independent of serological status and geographical site. However, the CD4 and CD8 T lymphocyte values obtained by the two methods are not interchangeable as IA compared to FC consistently gives higher percentage of CD4 T lymphocytes, and lower percentages of CD8 T lymphocytes. Mean differences between the two methods did not differ between the three African countries indicating that the IA method provides systematic results. Replicate measurements suggested good correspondence between results obtained by IA. By using an IA level of 〈 300 CD4 T lymphocytes/μl, the sensitivity was 81% and specificity 96% for detecting an FC level of 〈 200 CD4 T lymphocytes/μl. Using an IA level of 〈 20% CD4 T lymphocytes, the sensitivity was 89% and specificity 95% for detecting an FC level of 〈14% CD4 T lymphocytes, The FC and IA methods had the same internal correspondence between low absolute CD4 T cell counts and low CD4 percentages; the sensitivity and specificity for detecting a low absolute CD4 T cell count with a low CD4 percentage was 92% and 68% for FC and 91% and 73% for IA, respectively. The IA method is 10-fold cheaper than FC, is independent of advanced laboratory facilities, and does not need immediate processing of samples as blood smears can be stored for long periods. The IA method is therefore suitable for use in areas with limited resources and laboratory facilities where there is a need for immunological surveillance in hospital or community studies.
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  • 10
    ISSN: 0006-3592
    Keywords: bioreactor monitoring ; semi-on-line analysis ; aseptic sampling ; FIA ; SIA ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Monitoring of substrates and products during fermentation processes can be achieved either by on-line, in situ sensors or by semi-on-line analysis consisting of an automatic sampling step followed by an ex situ analysis of the retrieved sample. The potential risk of introducing time delays and signal bias during sampling makes it necessary to distinguish between real-time, on-line, in situ methods and semi-on-line analysis. In addition, semi-on-line analyzers are often mechanically complex - a circumstance which has to be given special attention during their industrial use on a routine basis. This review on semi-on-line analysis will focus both on the dynamics and precision of aseptic sampling devices and on the performance of flow injection analysis (FIA) and sequential injection analysis (SIA), especially with regard to their robustness when used in industry. © 1996 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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