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Minimum onset latency (Lmin) of single- and multiple-unit responses were mapped in the primary auditory cortex (AI) of barbiturate-anesthetized cats. Contralateral Lmin for multiple units was non-homogeneously distributed along the dorso-ventral/isofrequency axis of the AI. Responses with shorter latencies were more often located in the central, more sharply tuned region while longer latencies were more frequently encountered in the dorsal and ventral portions of the AI. For single units, a large scatter of Lmin values was found throughout the extent of the AI including cortical depth. The relationship between Lmin and previously reported spectral, intensity and temporal parameters was analyzed and revealed statistically significant correlations between minimum onset latency and the following response properties in some but not all studied animals: sharpness of tuning of a frequency response area 10 dB above threshold, broadband transient response, strongest response level, monotonicity of rate/level functions, dynamic range, and preferred frequency modulation sweep direction. This analysis suggests that Lmin is determined by several independent factors and that the prediction of Lmin based on relationships with other spectral and temporal response properties is inherently weak. The spatial distribution and the functional relationship between these response parameters may provide an important aspect of the time-based cortical representation of specific features in the animal's natural environment. 相似文献
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JA Koutcher AA Alfieri RL Stolfi ML Devitt JR Colofiore LD Nord DS Martin 《Canadian Metallurgical Quarterly》1993,53(15):3518-3523
The combination of N-(phosphonacetyl)-L-aspartate, 6-methylmercaptopurine, and 6-aminonicotinamide has been shown to be an effective antineoplastic regimen and also to enhance the effects of other chemotherapeutic agents. The mechanism of action of this combination of drugs is not known definitively, but one possible mechanism is biochemical modulation of energy metabolism and inhibition of production of tumor ATP. Tumor-bearing mice were treated with N-(phosphonacetyl)-L-aspartate, followed 17 h later by 6-methylmercaptopurine and 6-aminonicotinamide. 31P nuclear magnetic resonance spectroscopic studies demonstrated a significant depletion of high energy phosphates at 10 h post-6-methylmercaptopurine and 6-aminonicotinamide. The addition of radiation at this time was shown to induce a significantly longer tumor growth delay and a greater number of regressions (including durable complete regressions) than either chemotherapy or radiation alone. The combination of chemotherapy and radiation was found to be supra-additive compared to the antineoplastic effects of either modality administered separately, without a measurable increase in host toxicity. 相似文献
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Synthesis, absolute configuration, and analysis of malathion, malaoxon, and isomalathion enantiomers
Syntheses of the enantiomers of malathion, malaoxon, and isomalathion are reported herein. Malathion enantiomers were prepared from (R)- or (S)-malic acid in three steps. Enantiomers of malathion were converted to the corresponding enantiomers of malaoxon in 52% yield by oxidation with monoperoxyphthalic acid, magnesium salt. The four isomalathion stereoisomers were prepared via two independent pathways using strychnine to resolve the asymmetric phosphorus moiety. The absolute configurations of the four stereoisomers of isomalathion were determined by X-ray crystallographic analysis of an alkaloid salt precursor. A high-performance liquid chromatography technique was developed to resolve the four stereoisomers of isomalathion, and to determine their stereoisomeric ratios. 相似文献
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A complete and effective rehabilitation program begins with a thorough subjective and objective evaluation of the problem and injury presented. Biomechanical changes, whether they are anatomically induced or as a result of a form of compensation, must be identified and properly addressed. During the initial phase of rehabilitation, the issues of pain and swelling often must be resolved before full range of motion and return to normal strength can be achieved successfully during the more advanced stages. It is important to incorporate the entire lower quadrant in exercises that are designed to improve proprioception and function, using both in open and closed kinetic chain exercises. Finally, the demands to which the patient is returning to must be recognized to successfully complete the recovery phase. 相似文献
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CM Wheeler CA Parmenter WC Hunt TM Becker CE Greer A Hildesheim MM Manos 《Canadian Metallurgical Quarterly》1993,20(5):286-289
OBJECTIVES: To confirm the risk factors for genital human papillomavirus (HPV) infection. GOAL OF THIS STUDY: To investigate risk factors for HPV detection apart from the correlated risk factors for cervical neoplasia. STUDY DESIGN: Cervical human papillomavirus (HPV) DNA was assessed in 357 cytologically normal women attending the University of New Mexico student health center. Cervical swab samples were obtained for HPV DNA detection and typing using a PCR-based DNA amplification system. Possible determinants of cervical HPV were examined including age, ethnicity, history of sexually transmitted disease, oral contraceptive use, smoking, age at first intercourse, lifetime number of sex partners, marital status, and history of pregnancy. RESULTS: A 44.3% overall prevalence of cervical HPV was observed. On univariate analysis, factors associated with increasing HPV prevalence included higher lifetime number of sex partners and single marital status. After adjustment for potential confounding variables, we found that HPV prevalence increased with higher lifetime number of sexual partners. CONCLUSION: These findings, along with those from the companion reports in this issue of the journal, support the sexual route of transmission of the virus. 相似文献
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Two near-infrared spectroscopy (NIRS) methods are available for measuring changes (Delta) in total cerebral hemoglobin concentration (CHC): 1) a continuous measurement of the changes in total hemoglobin concentration (Delta[Hb]tot) and 2) the difference between two absolute measurements of CHC, each derived from a small, controlled change in inspired O2 fraction. This paper investigates the internal consistency of these two methods by using an experimental and theoretical comparison. NIRS was used to measure [Hb]tot in five newborn piglets before and after a change in arterial PCO2. Delta[Hb]tot demonstrated a low coefficient of variation of 2.8 +/- 2.8 (SD) % which allowed changes in CO2-cerebral blood volume reactivity to be clearly discriminated. However, a high coefficient of variation of 22.8 +/- 3.5% on the DeltaCHC measurements obscured any CO2 reactivity changes. A theoretical analysis demonstrates the effects of optical pathlength, background absorption, scatter, and blood vessel diameter on both methods. For more accurate monitoring of CHC, individual measurements of optical pathlength and more accurate pulse oximetry are required. 相似文献
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