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Precise Knowledge (precise + knowledge)
Selected AbstractsDecreased Tear Expression with an Abnormal Schirmer's Test Following Botulinum Toxin Type A for the Treatment of Lateral Canthal RhytidesDERMATOLOGIC SURGERY, Issue 2 2002Seth L. Matarasso MD background. Inactivation of muscles of facial expression by chemodenervation with botulinum toxin remains an off-label indication. Nevertheless, it continues to be a safe and effective technique to improve dynamic rhytides and is the treatment of choice for the hypertrophic lateral fibers of the orbicularis oculi muscle that can cause the superimposed crow's feet. objective. Although infrequent and self-limiting, the complication of unexpected muscle weakness from toxin diffusion or erroneous placement is documented. methods. However, injection into the pretarsal portion of the orbicularis oculi muscle resulting in unilateral ocular irritation and diminished tear expression as evidenced by a dry eye and an abnormal Schirmer's test has rarely been reported. Direct injection into the pretarsal fibers of the muscle as opposed to diffusion of the toxin into the muscle fibers or the lacrimal gland was consistent with the onset of action of the toxin and the prolonged duration of the ocular symptoms. results. Treatment consisted of ocular lubrication until the effects of the toxin dissipated and muscle tone returned. Subsequent treatment did not result in a result in a recurrence of adverse sequelae. conclusions. Facial muscles are small, not isolated, and often have fibers that interdigitate. An important factor in the administration of botulinum toxin is the identification of the muscles responsible for the corresponding rhytide. Precise knowledge of muscular anatomy and function will aid in minimizing this and other potential complications. [source] Regulation of virulence determinants in Staphylococcus aureus: complexity and applicationsFEMS MICROBIOLOGY REVIEWS, Issue 2 2004Stéphane Bronner Abstract The virulence of Staphylococcus aureus is essentially determined by cell wall associated proteins and secreted toxins that are regulated and expressed according to growth phases and/or growth conditions. Gene expression is regulated by specific and sensitive mechanisms, most of which act at the transcriptional level. Regulatory factors constitute numerous complex networks, driving specific interactions with target gene promoters. These factors are largely regulated by two-component regulatory systems, such as the agr, saeRS, srrAB, arlSR and lytRS systems. These systems are sensitive to environmental signals and consist of a sensor histidine kinase and a response regulator protein. DNA-binding proteins, such as SarA and the recently identified SarA homologues (SarR, Rot, SarS, SarT, SarU), also regulate virulence factor expression. These homologues might be intermediates in the regulatory networks. The multiple pathways generated by these factors allow the bacterium to adapt to environmental conditions rapidly and specifically, and to develop infection. Precise knowledge of these regulatory mechanisms and how they control virulence factor expression would open up new perspectives for antimicrobial chemotherapy using key inhibitors of these systems. [source] Precise knowledge of plant growth stages enhances applied and pure researchANNALS OF APPLIED BIOLOGY, Issue 2 2010S.R. Leather No abstract is available for this article. [source] Innervation of vastus lateralis muscleCLINICAL ANATOMY, Issue 5 2007S. Patil Abstract The lateral surgical approach to the proximal femur potentially damages the nerve supply to the vastus lateralis (VL) muscle. This study describes the detailed anatomy of the nerve supply to the VL muscle based on dissection of ten cadaveric lower limbs. In all specimens, a single nerve trunk arose from the femoral nerve, which is most subsequently divided into two main divisions. These divisions gave two branches each. These branches coursed from anteriorly and proximally to posteriorly and distally within the muscle. When the muscle was reflected anteriorly from its attachment to the linea aspera, there was no damage to its innervation. Splitting of the VL in the midlateral line of the femur, however, resulted in denervation of the posterior half of the muscle. Precise knowledge of the nerve supply to the VL will help avoid iatrogenic denervation of the muscle in surgical procedures at the proximal femur through the lateral approach. Clin. Anat. 20:556,559, 2007. © 2006 Wiley-Liss, Inc. [source] Febrile Seizures: Treatment and PrognosisEPILEPSIA, Issue 1 2000Finn Ursin Knudsen Summary: Recent epidemiologic data indicate that the vast majority of children with febrile seizures have a normal long-term outcome. A precise knowledge of the short- and long-term outcome with or without treatment, and short- and long-term side effects is an important prerequisite for assessing the various treatment strategies. We focus on the impact of short-term or prophylactic treatment on the short- and long-term outcome of various types of febrile seizures. There is universal agreement that daily prophylaxis with antiepileptic agents should never be used routinely in simple febrile seizures, but only in highly selected cases, if at all. Intermittent diazepam (DZP) prophylaxis at times of fever may or may not reduce the recurrence rate, but it does not appear to improve the long-term outcome as compared with short-term seizure control. The treatment may be used to reduce the recurrence rate for a small arbitrarily defined group with multiple simple febrile seizures, complex febrile seizures, especially focal, prolonged or both, febrile status, and when parental anxiety is severe. However, there is no evidence that treatment of simple febrile seizures can prevent the rare cases of later epilepsy, and many children with complex febrile seizures have a benign long-term outcome, even without treatment. Many prefer a "wait and see" policy. An attractive alternative is to treat new febrile seizures with rectal DZP in solution at seizure onset, given by the parents at home to prevent febrile status. Newer, less well documented short-term strategies include nasal, oral, or rectal administration of other benzodiazepines. Short-term seizure control of febrile status and careful parental counseling are the two most important targets of treatment. [source] Improving functional magnetic resonance imaging motor studies through simultaneous electromyography recordingsHUMAN BRAIN MAPPING, Issue 9 2007Bradley J. MacIntosh Abstract Specially designed optoelectronic and data postprocessing methods are described that permit electromyography (EMG) of muscle activity simultaneous with functional MRI (fMRI). Hardware characterization and validation included simultaneous EMG and event-related fMRI in 17 healthy participants during either ankle (n = 12), index finger (n = 3), or wrist (n = 2) contractions cued by visual stimuli. Principal component analysis (PCA) and independent component analysis (ICA) were evaluated for their ability to remove residual fMRI gradient-induced signal contamination in EMG data. Contractions of ankle tibialis anterior and index finger abductor were clearly distinguishable, although observing contractions from the wrist flexors proved more challenging. To demonstrate the potential utility of simultaneous EMG and fMRI, data from the ankle experiments were analyzed using two approaches: 1) assuming contractions coincided precisely with visual cues, and 2) using EMG to time the onset and offset of muscle contraction precisely for each participant. Both methods produced complementary activation maps, although the EMG-guided approach recovered more active brain voxels and revealed activity better in the basal ganglia and cerebellum. Furthermore, numerical simulations confirmed that precise knowledge of behavioral responses, such as those provided by EMG, are much more important for event-related experimental designs compared to block designs. This simultaneous EMG and fMRI methodology has important applications where the amplitude or timing of motor output is impaired, such as after stroke. Hum Brain Mapp 2006. © 2006 Wiley-Liss, Inc. [source] Mathematical modeling of 13C label incorporation of the TCA cycle: The concept of composite precursor functionJOURNAL OF NEUROSCIENCE RESEARCH, Issue 15 2007Kai Uffmann Abstract A novel approach for the mathematical modeling of 13C label incorporation into amino acids via the TCA cycle that eliminates the explicit calculation of the labeling of the TCA cycle intermediates is described, resulting in one differential equation per measurable time course of labeled amino acid. The equations demonstrate that both glutamate C4 and C3 labeling depend in a predictible manner on both transmitochondrial exchange rate, VX, and TCA cycle rate, VTCA. For example, glutamate C4 labeling alone does not provide any information on either VX or VTCA but rather a composite "flux". Interestingly, glutamate C3 simultaneously receives label not only from pyruvate C3 but also from glutamate C4, described by composite precursor functions that depend in a probabilistic way on the ratio of VX to VTCA: An initial rate of labeling of glutamate C3 (or C2) being close to zero is indicative of a high VX/VTCA. The derived analytical solution of these equations shows that, when the labeling of the precursor pool pyruvate reaches steady state quickly compared with the turnover rate of the measured amino acids, instantaneous labeling can be assumed for pyruvate. The derived analytical solution has acceptable errors compared with experimental uncertainty, thus obviating precise knowledge on the labeling kinetics of the precursor. In conclusion, a substantial reformulation of the modeling of label flow via the TCA cycle turnover into the amino acids is presented in the current study. This approach allows one to determine metabolic rates by fitting explicit mathematical functions to measured time courses. © 2007 Wiley-Liss, Inc. [source] Durable Goods Monopoly, Buyer Uncertainty, and Concurrent Selling and RentingMETROECONOMICA, Issue 4 2000Gregory E. Goering Stylized durable goods monopoly models typically conclude that monopolists prefer to rent their output due to commitment problems associated with sales. However, we commonly observe monopolistic firms in durable goods industries simultaneously selling and renting output. To address this apparent discrepancy a simple two-period asymmetric information model is constructed where buyers are uncertain of the good's durability and the firm's manufacturing costs. This is a natural asymmetric information specification since the firm typically has more precise knowledge of product durability and production costs than buyers do. The analysis indicates that a monopolist may wish to concurrently sell and rent output when buyers do not have perfect knowledge. If, for example, consumers believe that product durability and manufacturing costs are higher than they truly are, the firm may wish to simultaneously sell and rent output. Thus buyers' expectations about firm costs and product durability are of critical importance in durable goods models, particularly in terms of explaining concurrent rentals and sales. [source] Mammalian Sperm Energy Resources Management and Survival during Conservation in RefrigerationREPRODUCTION IN DOMESTIC ANIMALS, Issue 2006JE Rodriguez-Gil Contents The present review has as its main aim to present an overview regarding the mechanisms utilized by mammalian sperm to manage its intracellular energy levels. This management will strongly influence the sperm's ability to maintain its overall function during its entire life span. Thus, the precise knowledge of these mechanisms will be of the utmost interest to optimize the systems utilized to conserve mammalian sperm for a medium-to-long time-lapse. Briefly, utilization of hexoses as energy substrates by mammalian sperm is very finely regulated from the very first step of its metabolization. Furthermore, the equilibrium among the separate, monosaccharide metabolization pathways in mammalian sperm depends on many factors. This prevents the possibility to draw a general vision of sperm energy utilization, which explains the results of all mammalian species in all points of the sperm life-cycle. To complicate the matter further, there are separate energy phenotypes among mammalian spermatozoa. The precise knowledge of these phenotypes is of the greatest importance in order to optimize the design of new extenders for sperm conservation in refrigerated conditions. Moreover, sugars can act on sperm not only as passive metabolic substrates, but also as direct function activators through mechanisms like specific changes in the tyrosine phosphorylation status of distinct proteins. Finally, mammalian sperm utilizes non-glucidic substrates like citrate and lactate to obtain energy in a regular form. This utilization is also finely regulated and of importance to maintain overall sperm function. This implies that the exact proportion of glucidic and non-glucidic energy substrates could be very important to optimize the survival ability of these cells in conservation. [source] Bibliometric Methods: Pitfalls and PossibilitiesBASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 5 2005Johan A. Wallin Bibliometric indicators are strongly methodology-dependent but for all of them, various types of data normalization are an indispensable requirement. Bibliometric studies have many pitfalls; technical skill, critical sense and a precise knowledge about the examined scientific domain are required to carry out and interpret bibliometric investigations correctly. [source] Auswirkungen der Matrixzusammensetzung auf die Dauerhaftigkeit von Betonen mit textilen Bewehrungen aus AR-GlasBETON- UND STAHLBETONBAU, Issue 8 2009Marko Butler Dipl.-Ing. Baustoffe; Bewehrung; Versuche Abstract Verbundmaterialien aus Feinbetonen mit textiler Bewehrung aus alkaliresistentem Glas (AR-Glas) können ausgeprägten zeitabhängigen Veränderungen hinsichtlich des mechanischen Leistungsvermögens unterliegen. Für eine zielsichere Anwendung solcher Werkstoffe im Bauwesen sind genaue Kenntnisse über die Höhe und die Ursachen dieser Leistungsverluste unabdingbar. In diesem Artikel werden anhand von Ergebnissen aktueller Untersuchungen entscheidende Mechanismen für die Alterungsprozesse dargestellt, die aus der Zusammensetzung der Feinbetone resultieren. Dazu wurden aus verschiedenen Betonzusammensetzungen, die sich maßgeblich in ihrer Hydratationskinetik und Alkalität unterschieden, textilbewehrte Dehnkörper hergestellt und nach beschleunigter Alterung geprüft. Dehnkörper aus Feinbeton mit hoher Alkalität (das Bindemittel bestand nur aus CEM I) zeigten dramatische Einbußen bei Zugfestigkeit und Bruchdehnung. Das Leistungsvermögen von Proben aus Feinbetonen mit puzzolanisch abgepufferter Bindemittelzusammensetzung und gleichzeitig reduziertem Portlandzementklinkeranteil zeigte sich dagegen weitgehend unbeeinflusst von Alterungsprozessen. Mit Hilfe von beidseitigen Garnauszugversuchen an beschleunigt gealterten Feinbetonproben wurden die für das unterschiedliche Materialverhalten verantwortlichen Degradationsmechanismen aufgeklärt. Neben der mechanischen Prüfung wurde dazu auch die Interphase zwischen Fasern und umgebendem Feinbeton mit bildgebenden und analytischen Verfahren charakterisiert. Die festgestellten Einbußen im Leistungsvermögen des Garn-Matrix-Verbundes konnten überwiegend auf die Neubildung von ungünstig strukturierten Hydratationsprodukten in der Interphase Filament-Matrix bzw. in Filamentzwischenräumen zurückgeführt werden. Die Morphologie dieser Phase wird maßgeblich von der Bindemittelzusammensetzung bestimmt. Korrosion des AR-Glases als Schadensursache kann unter ungünstigen Umständen auch eine große Rolle spielen, ist aber bei geeigneter Matrixformulierung von untergeordneter Bedeutung. Effect of Matrix Composition on the Durability of Concretes Reinforced with Glass Fibre Fabric The mechanical performance of composites made of finegrained concrete and textile reinforcement can worsen markedly with increasing age if alkali-resistant glass (AR-glass) is used as the reinforcing material. For reliable practical applications of textile-reinforced concrete, precise knowledge as to the extent and causes of such degradation is indispensable. This paper discusses important aging mechanisms resulting from the composition of fine-grained concrete. Tensile tests on composites made of different concrete compositions distinguished from one another by their hydration kinetics and alkalinity were performed before and after accelerated aging. Composites made of concrete with high alkalinity showed dramatic losses of tensile strength and strain capacity. In contrast the mechanical performance of composites whose binders had reduced Portland cement clinker content plus added puzzolana was hardly affected by the accelerated aging. To clarify the mechanisms of degradation, yarn pullout tests were performed on specimens of equal matrix composition and age. Additionally, the morphology of the interphase between matrix and fibre was characterised using direct microscopic examination and analytical methods. The new formation of unfavourably structured products of hydration in the filament-matrix interphase and/or in the empty spaces between filaments was found to be the main reason for the performance losses observed. The morphology of these hydration products is determined to a great extent by the binder composition. Under unfavourable conditions corrosion of AR-glass can occur as well and lead to distinct composite damage. However, if the formulation of the binder is proper, bulk glass corrosion is of minor importance. [source] Iatrogenic vertebral artery injuryACTA NEUROLOGICA SCANDINAVICA, Issue 6 2005J. Inamasu Iatrogenic vertebral artery injury (VAI) results from various diagnostic and therapeutic procedures. The objective of this article is to provide an update on the mechanism of injury and management of this potentially devastating complication. A literature search was conducted using PubMed. The iatrogenic VAIs were categorized according to each diagnostic or therapeutic procedure responsible for the injury, i.e., central venous catheterization, cervical spine surgery, chiropractic manipulation, diagnostic cerebral angiography, percutaneous nerve block, and radiation therapy. The incidence, mechanisms of injury, and reparative procedures were discussed for each type of procedure. The type of VAI depends largely on the type of procedure. Laceration was the dominant type of acute injury in central venous catheterization and cervical spine surgery. Arteriovenous fistulae and pseudoaneurysms were the delayed complications. Arterial dissection was the dominant injury type in chiropractic manipulation and diagnostic cerebral angiography. Inadvertent arterial injection caused seizures or stroke in percutaneous nerve block. Radiation therapy was responsible for endothelial injury which in turn resulted in delayed stenosis and occlusion of the vertebral artery (VA). The proximal VA was the most vulnerable portion of the artery. Although iatrogenic VAIs are rare, they may actually be more prevalent than had previously been thought. Diagnosis of iatrogenic VAI may not always be easy because of its rarity and deep location, and a high level of suspicion is necessary for its early detection. A precise knowledge of the surgical anatomy of the VA is essential prior to each procedure to prevent its iatrogenic injury. [source] | |||||||||||||