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991.
Rabbit beta-globin is extended beyond its UGA stop codon by multiple suppressions and translational reading gaps 总被引:1,自引:0,他引:1
HS Chittum WS Lane BA Carlson PP Roller FD Lung BJ Lee DL Hatfield 《Canadian Metallurgical Quarterly》1998,37(31):10866-10870
Translational reading gaps occur when genetic information encoded in mRNA is not translated during the normal course of protein synthesis. This phenomenon has been observed thus far only in prokaryotes and is a mechanism for extending the reading frame by circumventing the normal stop codon. Reading frames of proteins may also be extended by suppression of the stop codon mediated by a suppressor tRNA. The rabbit beta-globin read-through protein, the only known, naturally occurring read-through protein in eukaryotes, was sequenced by ion trap mass spectrometry to determine how the reading frame is extended. Seven different proteolytic peptide fragments decoded by the same sequence that spans the UGA stop codon of rabbit beta-globin mRNA were detected. Three of these peptides contain translational reading gaps of one to three amino acids that correspond to the UGA stop codon site and/or one or two of the immediate downstream codons. To our knowledge, this is the first reported example of the occurrence of reading gaps in protein synthesis in eukaryotes. This event is unique in that it is associated with bypasses involving staggered lengths of untranslated information. Four of the seven peptides contain serine, tryptophan, cysteine, and arginine decoded by UGA and thus arise by suppression. Serine is donated by selenocysteine tRNA, and it, like the other tRNAs, has previously been shown to suppress UGA in vitro in mammals, but not in vivo. 相似文献
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993.
CA Reister SC Koenig JD Schaub DL Ewert RD Swope RD Latham JW Fanton 《Canadian Metallurgical Quarterly》1998,20(6):410-417
Investigative research efforts using a cardiovascular model required the determination of central circulatory haemodynamic and arterial system parameters for the evaluation of cardiovascular performance. These calculations required continuous beat-to-beat measurement of pressure within the four chambers of the heart and great vessels. Sensitivity and offset drift, longevity, and sources of error for eight 3F dual-tipped micromanometers were determined during 21 days of implantation in goats. Subjects were instrumented with pairs of chronically implanted fluid-filled access catheters in the left and right ventricles, through which dual-tipped (test) micromanometers were chronically inserted and single-tip (standard) micromanometers were acutely inserted. Acutely inserted sensors were calibrated daily and measured pressures were compared in vivo to the chronically inserted sensors. Comparison of the pre- and post-gain calibration of the chronically inserted sensors showed a mean sensitivity drift of 1.0 +/- 0.4% (99% confidence, n = 9 sensors) and mean offset drift of 5.0 +/- 1.5 mmHg (99% confidence, n = 9 sensors). Potential sources of error for these drifts were identified, and included measurement system inaccuracies, temperature drift, hydrostatic column gradients, and dynamic pressure changes. Based upon these findings, we determined that these micromanometers may be chronically inserted in high-pressure chambers for up to 17 days with an acceptable error, but should be limited to acute (hours) insertions in low-pressure applications. 相似文献
994.
Auditory event-related brain potentials (ERPs) were recorded during auditory and visual selective attention tasks. Auditory stimuli consisted of frequent standard tones (1000 Hz) and infrequent deviant tones (1050 Hz and 1300 Hz) delivered randomly to the left and right ears. Visual stimuli were vertical line gratings randomly presented on a video monitor at mean intervals of 6 s. During auditory attention, the subject attended to the stimuli in a designated ear and responded to the 1300-Hz deviants occurring among the attended tones. During visual attention, the subject responded to the occasional visual stimuli. ERPs for tones delivered to the attended ear were negatively displaced relative to ERPs elicited by tones delivered to the unattended ear and to ERPs elicited by auditory stimuli during visual attention. This attention effect consisted of negative difference waves with early and late components. Mismatch negativities (MMNs) were elicited by 1300-Hz and 1050-Hz deviants irrespective of whether they occurred among attended or unattended tones. MMN amplitudes were unaffected by attention, supporting the proposal that the MMN is generated by an automatic cerebral discrimination process. 相似文献
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The mechanism of biological effects of extremely-low-frequency electric and magnetic fields may involve induced changes of Ca2+ transport through plasma membrane ion channels. In this study we investigated the effects of externally applied, low-intensity 60 Hz electric (E) fields (0.5 V/m, current density 0.8 A/m2) on the agonist-induced Ca2+ fluxes of HL-60 leukemia cells. The suspensions of HL-60 cells received E-field or sham exposure for 60 min and were simultaneously stimulated either by 1 microM ATP or by 100 microM histamine or were not stimulated at all. After E-field or sham exposure, the responses of the intracellular calcium levels of the cells to different concentrations of ATP (0.2-100 microM) were assessed. Compared with control cells, exposure of ATP-activated cells to an E-field resulted in a 20-30% decrease in the magnitude of [Ca2+]i elevation induced by a low concentration of ATP (<1 microM). In contrast, exposure of histamine-activated HL-60 cells resulted in a 20-40% increase of ATP-induced elevation of [Ca2+]i. E-field exposure had no effect on non-activated cells. Kinetic analysis of concentration-response plots also showed that compared with control cells, exposure to the E-field resulted in increases of the Michaelis constant, Km, value in ATP-treated cells and of the maximal [Ca2+]i peak rise in histamine-treated HL-60 cells. The observed effects were reversible, indicating the absence of permanent structural damages induced by acute 60 min exposure to electric fields. These results demonstrate that low-intensity electric fields can alter calcium distribution in cells, most probably due to the effect on receptor-operated Ca2+ and/or ion channels. 相似文献
999.
SM Pear DL Goldsmith TH Williamson D Mandel GK Sethi DA Arzouman NM Ampel 《Canadian Metallurgical Quarterly》1998,19(7):513-515
A 74-year-old woman was referred to our hospital with the chief complaints of pneumaturia, fecaluria and discharge of feces and urine from vagina. Fistulography on the vaginal side showed the presence of contrast medium both in the sigmoid colon and bladder. Colonoscopy revealed multiple diverticulosis of the sigmoid colon. Under diagnosis of colo-vesico-vaginal fistula due to sigmoid colon diverticulitis, a one-stage operation removing sigmoid colon, uterus-vaginal wall and urinary bladder wall including the fistula and careful reconstruction was performed. Postoperatively, urinary leakage from vagina in large amounts continued due to the recurrence of vesico-vaginal fistula. An attempt to use human fibrin glue in the recurrent fistula was successful, and the patient was asymptomatic at 21 months of follow-up. Colovesical fistula has been reported in about 10-20% of patients undergoing surgery for complicated diverticulitis, but a combined fistula is a rare condition. Furthermore, we recommend the use of human fibrin glue for a recurrent fistula. 相似文献
1000.
With the diversity of our communities and waiting rooms increasing, can we continue to justify the lack of diversity among healthcare professionals? This article reports the demographic composition of the U.S. and compares those data with the professional healthcare workforce. With a non-White population of nearly 25%, only 10% of RNs are non-White and about 12% of medical students are non-White. Four reasons are presented for increasing diversity among healthcare professionals. These four include: improved culturally competent care, access to healthcare, healthcare outcomes and research, and provider access in high-need service areas. Healthcare organizations have gone on record as supporting increased diversity within high-skilled healthcare professions but without a commitment to increasing enrollments in professional healthcare programs, diversity goals will never be reached. 相似文献