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91.
Reports of the human teratogenicity of retinoids have raised concern about the potential human teratogenicity of high doses of vitamin A. Nevertheless, there are few human case reports of excess intake of vitamin A during pregnancy and defective outcomes. No epidemiological studies have been carried out on this subject. Here we present the results of an epidemiological study of prenatal exposure to high doses of vitamin A in Spain, using data from the Spanish hospital-based, case-control registry. Although it is difficult to reach conclusions with such a very low exposure level (1.3 per 1,000 livebirths), our results suggest that a teratogenic effect might exist for exposures to high doses of vitamin A (OR = 0.5, p = 0.15 for less than 40,000 FU and OR = 2.7, p = 0.06 for 40,000 1U or more). As we might expect, this effect also seems to be related to the organogenetic status (OR = 5.4, p = 0.1 for 1st –2nd month, OR = 1.8, p = 0.4 for 3rd onwards) at the time of exposure. 相似文献
92.
Jordi Llorens Cristina Su ol Josep M. Tusell Eduard Rodrí guez-Farr 《Neurotoxicology and teratology》1990,12(6):607-610
The inhibition of [35S]t-butylbicyclophosphorothionate ([35S]TBPS) binding to the GABAA receptor by the insecticide γ-hexachlorocyclohexane, lindane, was studied in several brain regions and using different membrane preparation methods, both in vitro and after dosing the animals with the chemical. In the latter studies, the amount of lindane remaining in the membrane suspensions used for binding assays was determined. In vitro data showed values of IC50 from 150 to 1675 nM, varying in function of the membrane preparation method used. This may account for the discrepancies in IC50 values found in the literature. IC50 values within the range of 150–250 nM were determined using extensively washed membranes from several brain regions, so no evidence arose for brain regional differences in the affinity of lindane for the TBPS binding site. After different schedules of acute treatment with lindane, we found a manifest relationship between the extent of the observable inhibition of [35S]TBPS binding and the lindane amount remaining in the membrane suspensions used for binding assays. This relationship was in good agreement with the in vitro data, so no support for an in vivo acute regulation of the binding site was obtained. 相似文献
93.
M. S. Lima F. Kallfelz L. Krook P. W. Nathanielsz 《Calcified tissue international》1993,52(4):283-290
Summary The objective of this study was to evaluate the effects of a long-term, low-calcium diet on fetal calcium metabolism and fetal
skeleton skeleton development in ewes. Eleven pregnant sheep were assigned to two groups, fed either a diet low in calcium
(0.26% total dry matter) or normal in calcium (0.8% total dry matter) for 2 months, starting at 60 days gestational age. The
ewes fed the low calcium diet showed lower plasma levels of calcium and higher plasma levels of hydroxyproline, parathyroid
hormone, and 1,25 (OH)2D compared with the ewes fed the normal calcium diet. There were no differences in these variables between the two groups
of fetuses. These observations suggest that the plasma components of calcium homeostasis measured in the fetal lamb in the
present study are independent of the ewe and are not significantly affected by the presence of lowere maternal calcium for
many weeks during pregnancy. Despite the ability of the fetus of the ewe on the low calcium diet to maintain relatively normal
circulating plasma components of calcium homeostasis, long-term maternal hypocalcemia delayed fetal skeletal ossification
as shown by histological examination of the fetal humerus. The fetal humerus from low calcium-fed ewes showed a lower proportion
of bone versus cartilage (45.6±5.9 versus 57.4±4.6%, mean ±SD) lower ash content (15.4±1.5 versus 17.4±1.0%), and lower specific
gravity (1.19±0.2 versus 1.22±0.02) (P<0.05) than the humerus from fetuses of normal calcium-fed ewes. This study shows that the long-term calcium intake of the
ewe does affect fetal skeletal development, despite a lack of observable effects on fetal plasma concentrations of calcium
or known calcium regulating hormones such as 1,25(OH)2D or parathyroid hormone. 相似文献
94.
微量元素锌在佝偻病治疗中的效果观察 总被引:7,自引:1,他引:6
目的 :探讨补充锌 +维生素D +钙剂治疗佝偻病的效果。方法 :随机分为 3组 ,每组各 5 3例。对照组给予常规治疗 (即维生素D +钙剂 ) ,治疗 1组先给予锌治疗 1个月后 +常规治疗 ,治疗 2组同时给予锌 +常规治疗。 3个月为 1疗程。治疗前后检测血清微量元素及骨碱性磷酸酶 (BALP)等项目。结果 :治疗 1、2组疗效好于对照组 ,差异非常显著 (P <0 0 1) ;治疗1组疗效好于治疗 2组 ,差异有显著性 (P <0 0 5 )。结论 :治疗大多数伴低锌的佝偻病先补锌 1个月 ,再加常规治疗 ,疗效更佳。 相似文献
95.
核黄素缺乏大鼠红细胞维生素E水平的变化及脂质过氧化关系的研究 总被引:6,自引:0,他引:6
对两组大鼠分别喂饲核黄素缺乏(RD)膳和核黄素添加(R8,22mg/kg饲料)膳8周后,测定了两组大鼠的红细胞维生素E(RBLVe)、红细胞超氧化物歧化酶(SOD)和红细胞丙二醛(MDA)的水平。结果发现:RD组RBCVe水平(4.7173±0.7710mg/g蛋白质)显著低于RS组(5。3868±1.1537mg/g蛋白质,P<0.05)。而RD组的RBCSOD(7745.2±610.1u/g蛋白质)和MDA(0.6868±0.1372μg/g蛋白质)则分别显著低于和高于RS组(8268.5±301.0nu/g蛋白质,0.5548±0.0980,P<0.05)。研究提示,核黄素缺乏引起细胞膜脂质过氧化加重可能RBCVe消耗增加。 相似文献
96.
作者用红细胞C_3b受体花环试验和红细胞免疫复合物花环试验对马桑内酯所致癫痫发作大鼠红细胞免疫粘附功能的变化进行了观察,结果表明,癫痫组动物红细胞C_3b受体花环率明显低于对照组,而红细胞免疫复合物花环率相差不显著.提示癫痫发作可导致大鼠红细胞免疫粘附功能降低,因此在癫痫治疗中注意调整和增强患者的红细胞免疫功能具有重要意义。 相似文献
97.
Enhanced stimulus-reward learning by intra-amygdala administration of a D3 dopamine receptor agonist
The amygdala is considered to be a critical neural substrate underlying the formation of stimulus-reward associations, and
is known to receive substantial innervation from dopaminergic neurons located within the ventral mesencephalon. However, relat-
ively little is known about the function of the mesoamygdaloid dopamine projection in stimulus-reward learning. Recently,
we have found post-session intra-amygdala microinjections of d-amphetamine to enhance appetitive Pavlovian conditioning as assessed in a discriminative approach task. In the present study,
we have examined the effects of dopamine receptor agonists possessing relative selectivity for the D1, D2 and D3 receptor subtypes in order to examine more fully the role of the mesoamygdaloid dopamine projection in stimulus-reward learning.
Thus, subjects were trained to associate an initially neutral stimulus (CS+) with 10% sucrose reward (US). A second, control stimulus (CS−) was also presented but never paired with sucrose reward. In order to measure specifically the conditioned response to CS+/CS− presentation, responding during CS and US presentations was measured separately. Immediately following each training session,
subjects received bilateral intra-amygdala infusion of 0.1, 1 or 10 nmol/side of SKF-38393, quinpirole or 7-OH-DPAT. Infusions
of SKF-38393 or quinpirole were without effect on CS+ approach. However, post-session intra-amygdala infusions of 7-OH-DPAT enhanced selectively CS+ approach in a dose-dependent fashion. No dose of any drug affected CS−approach, US behaviours, or measures of extraneous behaviour. Subsequent acquisition of a novel conditioned instrumental response
was also unaffected. Thus, the present data indicate a selective involvement of the D3 dopamine receptor subtype in the modulation of stimulus-reward learning by the mesoamygdaloid dopamine projection.
Received: 12 December 1996 / Final version: 9 April 1997 相似文献
98.
Simon Vinitski Carlos Gonzalez Feroze Mohamed Tad Iwanaga Robert L. Knobler Kamil Khalili John Mack 《Magnetic resonance in medicine》1997,37(3):457-469
Our aim was to develop an accurate multispectral tissue segmentation method based on 3D feature maps. We utilized proton density (PD), T2-weighted fast spin-echo (FSE), and T1-weighted spin-echo images as inputs for segmentation. Phantom constructs, cadaver brains, an animal brain tumor model and both normal human brains and those from patients with either multiple sclerosis (MS) or primary brain tumors were analyzed with this technique. Initially, misregistration, RF inhomogeneity and image noise problems were addressed. Next, a qualified observer identified samples representing the tissues of interest. Finally, k-nearest neighbor algorithm (k-NN) was utilized to create a stack of color-coded segmented images. The inclusion of T1 based images, as a third input, produced significant improvement in the delineation of tissues. In MS, our 3D technique was found to be far superior to that based on any combination of 2D feature maps (P < 0.001). We identified at least two distinctly different classes of lesions within the same MS plaque, representing different stages of the disease process. Further, we obtained the regional distribution of MS lesion burden and followed its changes over time. Neuropsychological aberrations were the clinical counterpart of the structural changes detected in segmentation. We could also delineate the margins of benign brain tumors. In malignant tumors, up to four abnormal tissues were identified: 1) a solid tumor core, 2) a cystic component, 3) edema in the white matter, and 4) areas of necrosis and hemorrhage. Subsequent neurosurgical exploration confirmed the distribution of tissues as predicted by this analysis. 相似文献
99.
重症肌无力病人乙酰胆碱受体抗体的测定及临床意义 总被引:7,自引:0,他引:7
用ELISA(固相酶联免疫吸附)法测定172例MG病人血清乙酰胆碱受体抗体(AchRab),结果显著高于健康献血员组和非MG病人组。不同性别、病程及临床类型与AchRab无相关性,但41~50岁组的显著高于其他年龄组。67例类固醇激素治疗组、22例大剂量两种球蛋白治疗组、12例胸腺切除术组及3例MG危象病人24次血浆交换疗法(PE)组,治疗后伴随肌无力症状的好转,AchRab均显著低于治疗前。结果表明:AchRab测定为MG诊断提供了可靠的实验依据,为类固醇激素、大剂量丙种球蛋白、胸腺切除术和PE等治疗MG提供理论依据和疗效评定的实验指标,进一步证实了MG免疫学发病机理。 相似文献
100.
Intrastriatal injection of the GABAA antagonist, bicuculline, caused about a 75% decrease in the inhibitory effect of the central-type benzodiazepine (BZ) agonist, clonazepam or the indoleamine hormone, melatonin, on apomorphine-induced rotation in a 6-hydroxydopamine model of dopaminergic supersensitivity. Pretreatment with the peripheral-type BZ antagonist, PK 11195 (intrastriatally or intraperitoneally), also attenuated the antidopaminergic effect of these drugs but with much less potency than bicuculline. However, the combination of both bicuculline and PK 11195, injected directly into the striatum, completely blocked the antidopaminergic action of clonazepam or melatonin. These results indicate that the antidopaminergic action of clonazepam and melatonin in the striatum involves two distinct mechanisms: (1) a predominant GABAergic activation via the BZ/GABAA receptor complex, and (2) a secondary mechanism linked to a PK 11195- sensitive BZ receptor pathway. Recent studies indicate that PK 11195 blocks BZ-induced inhibition of the adenylyl cyclase-cyclic AMP pathway in the striatum. Since cyclic AMP has been implicated in the rotational behaviour of 6-hydroxydopamine-lesioned animals, it is possible that the antidopaminergic action of clonazepam and melatonin also involves suppression of this second messenger. All rights reserved. 相似文献