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721.
The recent progress in molecular biology research has changed the past concepts on Alzheimer's disease (AD) and other nervous system amyloidoses. This paper compiles the basic principles of molecular biology of AD and reviews their clinical impact The new data about the function and metabolism of amyloid precursor protein and the more recent information on the role of the apolipoprotein E have provided new insight into the pathogenesis of this disease. Although further investigations are still required to assemble these data into a theory that completely explains the development of the disease and changes the present symptomatic therapeutic strategies to an entire preventive or curative approach, the recent research results in this field are relevant for the diagnostic and therapeutic management of AD patients. 相似文献
722.
723.
724.
Enzymes involved in the bioactivation of 4-(methylnitrosamino)-1-(3- pyridyl)-1-butanone in patas monkey lung and liver microsomes 总被引:1,自引:2,他引:1
4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is a potent
tobacco-specific carcinogen in animals. Our previous studies indicated that
there are differences between rodents and humans for the enzymes involved
in the activation of NNK. To determine if the patas monkey is a better
animal model for the activation of NNK in humans, we investigated the
metabolism of NNK in patas monkey lung and liver microsomes and
characterized the enzymes involved in the activation. In lung microsomes,
the formation of 4-oxo-1-(3-pyridyl)-1-butanone (keto aldehyde),
4-(methylnitrosamino)-1-(3-pyridyl-N-oxide)-1-butanone (NNK- N-oxide),
4-hydroxy-1-(3-pyridyl)-1-butanone (keto alcohol), and 4-
(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) was observed, displaying
apparent Km values of 10.3, 5.4, 4.9, and 902 microM, respectively. NNK
metabolism in liver microsomes resulted in the formation of keto aldehyde,
keto alcohol, and NNAL, displaying apparent Km values of 8.1, 8.2, and 474
microM, respectively. The low Km values for NNK oxidation in the patas
monkey lung and liver microsomes are different from those in human lung and
liver microsomes showing Km values of 400-653 microM, although loss of low
Km forms from human tissue as a result of disease, surgery or anesthesia
cannot be ruled out. Carbon monoxide (90%) significantly inhibited NNK
metabolism in the patas monkey lung and liver microsomes by 38-66% and
82-91%, respectively. Nordihydroguaiaretic acid (a lipoxygenase inhibitor)
and aspirin (a cyclooxygenase inhibitor) decreased the rate of formation of
keto aldehyde and keto alcohol by 10-20 % in the monkey lung microsomes.
Alpha-Napthoflavone and coumarin markedly decreased the oxidation of NNK in
monkey lung and liver microsomes, suggesting the involvement of P450s 1A
and 2A6. An antibody against human P450 2A6 decreased the oxidation of NNK
by 12-16% and 22-24% in the patas monkey lung and liver microsomes,
respectively. These results are comparable to that obtained with human lung
and liver microsomes. Coumarin hydroxylation was observed in the patas
monkey lung and liver microsomes at a rate of 16 and 4000 pmol/min/mg
protein, respectively, which was 5-fold higher than human lung and liver
microsomes, respectively. Immunoblot analysis demonstrated that the P450 2A
level in the individual patas monkey liver microsomal sample was 6-fold
greater than in an individual human liver microsomal sample. Phenethyl
isothiocyanate, an inhibitor of NNK activation in rodents and humans,
decreased NNK oxidation in the monkey lung and liver microsomes displaying
inhibitor concentration resulting in 50% inhibition of the activity (IC50)
values of 0.28-0.8 microM and 4.2-6.8 microM, respectively. The results
demonstrate the similarities and differences between species in the
metabolic activation of NNK. The patas monkey microsomes appear to more
closely resemble human microsomes than mouse or rat enzymes and may better
reflect the activation of NNK in humans.
相似文献
725.
Promotion of dimethylbenz[a]anthracene-initiated mammary carcinogenesis by iron in female Sprague-Dawley rats 总被引:1,自引:0,他引:1
Iron body-stores and iron dietary intake have been sporadically reported to
increase the risk of cancer in humans. To investigate the effect of iron on
the development of mammary tumors, female Sprague- Dawley rats were given
dimethylbenz[a]anthracene (DMBA) (5 mg/kg, i.g., 1x) at 55 days of age.
Eight days later, rats received iron(II) sulfate s.c. (50 micromol/kg,
2x/week) for 53 weeks. Mammary tumors started to appear 6-8 weeks after
DMBA initiation. At 20 weeks after DMBA treatment, iron(II) increased
mammary tumor frequency twofold (11/30 versus 5/30 with DMBA alone). Tumor
frequency increased with time and was significantly higher in iron-promoted
rats after 40 weeks of treatment (24/30 versus 11/30, P = 0.001). Also,
mammary tumors in iron- promoted rats were significantly larger than in
DMBA-only rats at 20 weeks after initiation (P = 0.04) and this difference
remained significant through the observation time point at 40 weeks. Iron
could be detected histochemically in the stromal connective tissue, but not
in the epithelial cells of mammary carcinomas. Mammary tumors in the
DMBA-only group were mostly adenomas and adenocarcinomas, while those
promoted by iron sulfate included fibroadenomas, adenomas and
adenocarcinomas. Thus, iron(II) administered s.c. subsequent to DMBA
initiation, greatly accelerated mammary carcinogenesis, implying its
promoting activity for mammary tissue of female rats.
相似文献
726.
Emiliano Calvo Aller Ramón Arcas Meca Aurora Crespo de la Jara Antonio Brugarolas Masllorens Timo LM ten Hagen Alexander MM Eggermont 《Clinical & translational oncology》2003,5(3):128-138
Resumen La perfusión de extremidad aislada (PEA) con melfalán es activa en el tratamiento de las metástasis en tránsito de melanoma,
pero no ha mostrado eficacia en el de sarcomas de partes blandas irresecables de extremidad. Esta situación se ha visto modificada
con la aparición del factor de necrosis tumoral-α (TNF), fármaco que destruye la vasculatura tumoral y aumenta de tres a 6
veces la captación selectiva de otros medicamentos por el tumor. Actualmente está demostrado que la PEA con TNF más melfalán
es una modalidad terapéutica muy exitosa en ambas indicaciones para prevenir la amputación del miembro afecto. También hay
datos contrastados sobre la eficacia de este régimen en tumores cutáneos multifocales y sarcomas óseos refractarios.
相似文献
727.
In urea kinetic modeling, postdialysis blood urea nitrogen (BUN) is usually underestimated with an overestimation of the Kt/V especially in high-efficiency hemodialysis (HD). Thus, an artificial neural network (ANN) was used to predict the equilibrated BUN (Ceq) and equilibrated Kt/V (eKt/V60) by using both predialysis, postdialysis, and low-flow postdialysis BUN. The results were compared to a Smye formula to predict Ceq and a Daugirdas' formula (eKt/V30) to predict eKt/V60. Seventy-four patients on high-efficiency or high-flux HD were recruited. Their mean urea rebound was 28.6+/-2%. Patients were divided into a "training" set (n = 40) and a validation set (n = 34) for the ANN. Their status was exchanged later, and the two results were pooled. In the prediction of Ceq, both Smye formula and low-flow ANN were equally highly accurate. In patients with a high urea rebound (>30%), although Smye formula lost its accuracy, low-flow ANN remained accurate. In the prediction of eKt/V60, both Daugirdas' formula and low-flow ANN were equally accurate, although the Smye formula was not so accurate. In patients with a high urea rebound, although both Smye and Daugirdas' formulas lost their accuracy, low-flow ANN remained accurate. We concluded that low-flow ANN can accurately predict both Ceq and eKt/V60 regardless of the degree of urea rebound. 相似文献
728.
LM Irgens T Markestad V Baste P Schreuder R Skjaerven N Oyen 《Archives of disease in childhood》1995,72(6):478-482
OBJECTIVE--To investigate, in a population based national study, the association between sleeping position of infants and the occurrence of sudden infant death syndrome (SIDS). DESIGN--A retrospective survey and registry based ecological study. A questionnaire based surveillance of sleeping position was obtained in a random sample (n = 34,799) and surveillance of SIDS was based on all infants born in Norway 1967-91, surviving the perinatal period. Variables studied from the questionnaire were usual sleeping position (placed), breast feeding at 3 months, and maternal smoking in pregnancy, and from the Medical Birth Registry maternal age, birth order, and birth weight. RESULTS--Proportion of infants sleeping prone increased from 1970 (7.4%) to 1989 (49.1%) and dropped in 1990 (26.8%) and 1991 (28.3%). Occurrence of SIDS increased from 1970 (1.1/1000) to 1989 (2.0) before dropping in 1990 and 1991 (1.1). IMPLICATION AND RELEVANCE OF RESULTS--A cause effect relationship between prone sleeping and SIDS as suggested in previous studies is supported by the present; and so far only, national study of infants' sleeping position. 相似文献
729.
B Alm J Milerad G Wennergren R Skjaerven N Oyen G Norvenius AK Daltveit K Helweg-Larsen T Markestad LM Irgens 《Archives of disease in childhood》1998,78(4):329-334
AIM: To establish whether smoking is an independent risk factor for sudden infant death syndrome (SIDS), if the effect is mainly due to prenatal or postnatal smoking, and the effect of smoking cessation. METHODS: The analyses were based on data from the Nordic epidemiological SIDS study, a case-control study with 244 cases and 869 controls. Odds ratios were computed by conditional logistic regression analysis. RESULTS: Smoking emerged as an independent risk factor for SIDS, and the effect was mainly mediated through maternal smoking in pregnancy (crude odds ratio 4.0 (95% confidence interval 2.9 to 5.6)). Maternal smoking showed a marked dose-response relation. There was no effect of paternal smoking if the mother did not smoke. Stopping or even reducing smoking was beneficial. SIDS cases exposed to tobacco smoke were breast fed for a shorter time than non-exposed cases, and feeding difficulties were also more common. CONCLUSIONS: Smoking is an independent risk factor for SIDS and is mainly mediated through maternal smoking during pregnancy. Stopping smoking or smoking less may be beneficial in reducing the risk of SIDS. 相似文献
730.
A total of 121 infants entered a cohort serological study of primary infections with herpes-viruses. All of them had seven samples of blood available: the first sample was taken soon after birth, the other six were taken at 1, 2, 3, 6, 12, and 14 months of age. One sample of maternal blood was collected immediately after delivery. All blood samples were tested for antibodies against cytomegalovirus, Epstein-Barr virus, and human herpesvirus-6 (HHV-6). Primary cytomegalovirus infection occurred early; the cumulative infection rates were 1.7%, 8.3%, 18.3%, 25%, 52.5%, and 65% by the ages of 1, 2, 3, 6, 12, and 14 months, respectively. Epstein-Barr virus infection was not seen before 3 months of age and slowly emerged thereafter, reaching a cumulative rate of 1.7%, 11.6%, 21.5% at the ages of 6, 12, and 14 months, respectively. Primary HHV-6 infection was also a rare event in the first three months of life, but peaked between 6 and 12 months of age. No detectable risk factors were associated with primary Epstein-Barr virus or HHV-6 infection. The risk factors associated with cytomegalovirus infection included breast feeding, fewer children in household, and care by a babysitter. 相似文献