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991.
Detection and measurement of PCR bias in quantitative methylation analysis of bisulphite-treated DNA
PM Warnecke C Stirzaker JR Melki DS Millar CL Paul SJ Clark 《Canadian Metallurgical Quarterly》1997,25(21):4422-4426
Methylation analysis of individual cytosines in genomic DNA can be determined quantitatively by bisulphite treatment and PCR amplification of the target DNA sequence, followed by restriction enzyme digestion or sequencing. Methylated and unmethylated molecules, however, have different sequences after bisulphite conversion. For some sequences this can result in bias during the PCR amplification leading to an inaccurate estimate of methylation. PCR bias is sequence dependent and often strand-specific. This study presents a simple method for detection and measurement of PCR bias for any set of primers, and investigates parameters for overcoming PCR bias. 相似文献
992.
The reorganization of neural activity that takes place after stroke is of paramount importance in producing functional recovery. Experimental stroke models have suggested that this reorganization may have two phases, but physiology alone cannot fully resolve what causes each phase. Computer modeling suggests that these phases might involve an initial change in dynamics occurring immediately, followed by synaptic plasticity. We combined physiological recording from macaque middle temporal cortex (area MT) with a neural network computer model to examine this first phase of altered cortical function after a small, experimentally induced cortical lesion. Major receptive field (RF) changes seen in the first few days postlesion included both expansion and contraction of receptive fields. Although only expansion could be reproduced in an initial model, addition of inhibitory interneuron loss in a ring around the primary ablation, suggested by immunohistochemical examination, permitted contraction to be replicated as well. We therefore predict that this immunochemical observation reflects an immediate extension of the lesion rather than a late response. Additionally our model successfully predicted a correlation between increased firing rate and RF size. Our model suggests that activation dynamics alone, without anatomic remodeling, can cause the large receptive field changes that allow the rapid behavioral recovery seen after middle temporal lesions. 相似文献
993.
994.
A target that is nearer to one eye than the other subtends a larger visual angle in the closer eye. Consequently, when making saccades between vertically separated targets that are closer to one eye, there is a vertical retinal disparity that must be overcome by a change in the relative alignment of the eyes. We recorded eye movements in three normal subjects and showed that in such viewing circumstances subjects made unequal vertical saccades that led to a rapid change (peak velocity up to 30 deg/sec) in vertical eye alignment. On average, 81% of the required change in alignment occurred within the saccade for downward movements and 47% for upward movements. Such unequal vertical saccades occurred independently of immediate disparity cues; saccades remained unequal when refixing to the remembered locations of the vertically-oriented targets, or even when the natural vertical disparity was nullified by a prism. On the other hand, when subjects wore the nullifying prism in front of the inferior visual field of the left eye for 8-20 hr, they showed a decrease in saccade disconjugacy (to 12-35% of the preadaptation value) to targets closer to the left eye in the inferior but not in the superior visual field. We suggest that the brain develops a three-dimensional map (horizontal, vertical, depth) for vertical saccade yoking, which is under adaptive control, and which is used to preprogram automatically the relative excursions of the eyes during vertical saccades as a function of the current and the desired point of regard. 相似文献
995.
DS Zern 《Canadian Metallurgical Quarterly》1997,158(1):79-95
A questionnaire-based study of 2,863 adolescents (ages 12 to 22 years), with data collected over 15 years, measured the extent to which informants believed that elementary, secondary, and college-age young people should receive guidance on moral issues from the family, school, clergy, peers, and/or the individual himself or herself. Averaging the ratings of all respondents over the first three categories yielded an overall authority score of 1.85, where a score of 2.00 represented a belief in moderate influence. Results showed a minimal difference in the ratings between genders, among different age groups, and across the different calendar years of questionnaire administration. Much more substantial differences existed among the actual influences investigated and across the ages of those to whom the influence was to be directed. 相似文献
996.
Coccidial parasites of the genus Isospora cause intestinal disease in several mammalian host species. These protozoal parasites have asexual and sexual stages within intestinal cells of their hosts and produce an environmentally resistant cyst stage, the oocyst. Infections are acquired by the ingestion of infective (sporulated) oocysts in contaminated food or water. Some species of mammalian Isospora have evolved the ability to use paratenic (transport) hosts. In these cases, infections can be acquired by ingestion of an infected paratenic host. Human intestinal isosporiasis is caused by Isospora belli. Symptoms of I. belli infection in immunocompetent patients include diarrhea, steatorrhea, headache, fever, malaise, abdominal pain, vomiting, dehydration, and weight loss, blood is not usually present in the feces. The disease is often chronic, with parasites present in the feces or biopsy specimens for several months to years. Recurrences are common, Symptoms are more severe in AIDS patients, with the diarrhea being more watery. Extraintestinal stages of I. belli have been observed in AIDS patients but not immunocompetent patients. Treatment of I. belli infection with trimethoprim-sulfamethoxazole usually results in a rapid clinical response. Maintenance treatment with trimethoprim-sulfamethoxazole is needed because relapses often occur once treatment is stopped. 相似文献
997.
AD Harries DS Nyangulu C Kangombe D Ndalama JJ Wirima FM Salaniponi G Liomba D Maher P Nunn 《Canadian Metallurgical Quarterly》1997,91(7):771-776
Malawi is similar to a number of other African countries in having an escalating, HIV-related, tuberculosis (TB) epidemic. A prospective study was carried out to determine the pattern of disease and HIV serostatus in unselected, adult, TB patients consecutively admitted to a large, district general hospital in Zomba (in the Southern region of Malawi). Clinical details were obtained, from the district TB register, for the 714, adult TB patients, aged > or = 15 years, who were registered with the district TB officer between 1 July and 31 December in 1995. Patients were counselled, and offered HIV testing using an ELISA and particle agglutination test. Concordant HIV-test results were available for 686 (96%) of the subjects: 547 (80%) of these were HIV-seropositive and 139 seronegative. The HIV-positive patients were significantly younger than the HIV-negative patients and significantly more HIV-positive patients were males (P < 0.05 for each). The proportions of HIV-positive subjects who were new patients, had been previously treated for TB, had pulmonary TB (PTB), had smear-positive PTB or had different types of extrapulmonary TB were similar to those of the HIV-negative. A high percentage of an unselected cohort of adult TB patients admitted to a district, general hospital in Malawi, particularly of the younger age groups was therefore HIV-positive. The pattern of disease was uninfluenced by the HIV serostatus. The large number of cases registered emphasises the severity of the current epidemic of TB in Malawi and its impact upon young adults. 相似文献
998.
The central administration of cholinergic agonists can produce a significant increase in arterial blood pressure by enhancing sympathetic vasomotor tone. The stimulation of spinal muscarinic receptors through intrathecal (i.t.) injection of carbachol in rats evoked a significant pressor response that returned to preinjection levels within 30 to 40 min. We investigated the roles of glutamatergic and GABAergic receptors in mediating the hypertensive response to i.t. injection of the muscarinic receptor agonist carbachol and in the maintenance of resting blood pressure and heart rate. The i.t. pretreatment with the N-methyl-D-aspartate (NMDA) receptor antagonists D-AP7 or MK801 maleate (dizocilipine) attenuated the pressor response to i.t. administration carbachol in a dose-dependent manner in conscious, freely moving rats. In contrast, i.t. pretreatment with 6-cyano-7-nitroquinoxaline-2,3-dione, a non-NMDA glutamate receptor antagonist, was not effective in this regard, indicating that the carbachol-evoked pressor response was not mediated through the quisqualate/kainate subtype of glutamate receptors. The i.t. pretreatment with the gamma-aminobutyric acid type B receptor agonist baclofen also inhibited the pressor response to i.t. injection of carbachol at doses that did not alter motor function. To determine whether the pressor response to stimulation of spinal muscarinic receptors required the participation of higher centers, rats received an intracisternal injection of either methylatropine or D-AP7 before the i.t. injection of carbachol. Both intracisternal pretreatments significantly reduced the expression of the pressor response to i.t. injection of carbachol. These findings are consistent with the presence of a powerful modulating spinobulbar muscarinic pressor system. Pharmacological activation of this system involves the participation of spinal and perhaps medullary glutamate-NMDA and gamma-aminobutyric acid type B receptor systems. 相似文献
999.
LH Xu X Wang TJ Cronin DS Perry GT Fraser AS Pine 《Canadian Metallurgical Quarterly》1997,185(1):158-172
The infrared spectrum of jet-cooled methanol in the CH-stretch fundamental region has been investigated by two sub-Doppler laser techniques: optothermally detected molecular-beam electric resonance and direct-absorption slit-jet spectroscopy. With the aid of microwave-infrared double resonance and ground state combination differences, 27 subbands in the frequency range 2967 to 3027 cm-1 have been assigned to the nu2 fundamental. Perturbation systems in the K' = 0 E, -1 E, and -2 E symmetry subbands have been analyzed to yield matrix elements of 0.013, 0.041, and 0.75 cm-1, respectively. The A-E torsional tunneling splitting for J = 0 of the nu2 vibration of -3.26 cm-1 is of opposite sign and a factor of three smaller in magnitude than the ground state value of +9.12 cm-1. Copyright 1997 Academic Press. Copyright 1997Academic Press 相似文献
1000.