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排序方式: 共有1578条查询结果,搜索用时 8 毫秒
991.
Atherosclerotic renal artery stenosis: ostial or truncal? 总被引:4,自引:0,他引:4
Kaatee R; Beek FJ; Verschuyl EJ; v.d. Ven PJ; Beutler JJ; van Schaik JP; Mali WP 《Radiology》1996,199(3):637
992.
993.
Female pelvic floor: endovaginal MR imaging of normal anatomy 总被引:4,自引:0,他引:4
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997.
Age and menopausal status were evaluated as potential modulators of the
progesterone action in the initiation of the mid-cycle luteinizing hormone
(LH) surge in women. Three distinct levels of oestradiol priming were used,
in combination with two different two-step ranks of progesterone
stimulation (10/25 mg and 25/50 mg i.m. injections of progesterone in oil,
over 2 consecutive days) in two groups of women, ten premenopausals, aged
between 18 and 25 years, and 14 postmenopausals, aged between 48 and 57
years. The low, moderate and high levels of oestradiol priming were defined
in the premenopausal group by days 5 and 9 of the cycle, and 0.4 mg
transdermal oestradiol applied in the early follicular phase respectively.
The corresponding situation in the postmenopausal women was defined by the
absence of treatment, 0.1 mg transdermal oestradiol, and 0.4 mg transdermal
oestradiol respectively. The oestradiol patches were maintained for 5 days,
and the first progesterone dose administered on day 3 of treatment.
Unambiguous LH surges, detected in serum and urine, were restricted to the
protocols using 0.4 mg oestradiol in both groups, with an onset soon after
progesterone administration. The surge was higher in the postmenopausal
group in serum and urine. The percentage LH increase above baseline,
however, was higher in the premenopausal women. The dose of progesterone
did not result in any changes in pituitary LH release. Therefore, the
oestradiol threshold for the progesterone stimulatory effect on LH release
was similar in both groups. The postmenopausal women did not yield
defective LH surges when adequately primed with oestradiol and
progesterone.
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1000.
Age-related differences in distractibility and response to methylphenidate in monkeys 总被引:2,自引:0,他引:2
Prendergast MA; Jackson WJ; Terry AV Jr; Kille NJ; Arneric SP; Decker MW; Buccafusco JJ 《Cerebral cortex (New York, N.Y. : 1991)》1998,8(2):164-172
Increased susceptibility to distraction is a symptom of normal aging and
several clinical syndromes, including Alzheimer's disease and attention
deficit disorders. In the present study, aged and young adult macaques were
well-trained to perform an automated delayed matching-to- sample (DMTS)
task which assesses both attention and short-term memory. On 19% of all
trials, a task-relevant distracting stimulus was presented during either
the initial 1 or 3 s of delay intervals (early onset) or the final 1 or 3 s
of delay intervals (late onset). In aged monkeys, both early and late onset
distractors lasting 1 or 3 s impaired delayed recall on trials with the
shortest delay intervals, but did not affect accuracy on trials with long
delay intervals. In contrast, young adult monkeys were impaired only by the
presence of an early onset distractor lasting 3 s. Impairment was selective
for only those trials with the shortest delay intervals. Late onset
distractors were relatively ineffective in producing distractibility in
young adult animals. Methylphenidate (MPH; 0.005-1.0 mg/kg) failed to
reduce distractibility in aged monkeys, producing locomotor abnormalities
and hypophagia at doses ranging from 0.25 to 1.0 mg/kg. In young adult
monkeys, however, distractibility was significantly attenuated by
administration of the 0.125 mg/kg dose. Habituation to the distracting
stimulus (under saline conditions) was assessed throughout the study and
was not evident at any time point of testing. These data indicate that
attention and recall after brief delays are impaired following exposure to
a task-relevant distracting stimulus in both aged and young adult monkeys,
but that aged monkeys are more susceptible to distraction and do not
receive significant benefit from MPH administration.
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