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51.
M A Nowak S Bonhoeffer R M May 《Proceedings of the National Academy of Sciences of the United States of America》1994,91(11):4877-4881
The Prisoner's Dilemma (PD) is a widely employed metaphor for problems associated with the evolution of cooperative behavior. We have recently proposed an alternative approach to the PD, by exploring "spatial games" in which players--who are either pure cooperators, C, or pure defectors, D--interact with neighbors in some spatial array; in each generation, players add up the scores from all encounters, and in the next generation a given cell is retained by its previous owner or taken over by a neighbor, depending on who has the largest score. Over a wide range of the relevant parameters, we find that C and D persist together indefinitely (without any of the complex strategies that remember past encounters, and anticipate future ones, which characterize essentially all previous work on the iterated PD). Our earlier work, however, dealt with symmetric spatial lattices in two dimensions, deterministic winning and discrete time. We show here that the essential results remain valid in more realistic situations where the spatial distributions of cells are random in two or three dimensions, and where winning is partly probabilistic (rather than being determined by the largest local total). The essential results also remain valid (pace Huberman and Glance [Huberman, B. A. & Glance, N. S. (1993) Proc. Natl. Acad. Sci. USA 90, 7716-7718]) when interactions occur in continuous rather than discrete time. 相似文献
52.
53.
Two cases of familial form (in brothers) of extensive, symmetric, idiopathic calcifications of the basal ganglia and cerebellum (Fahr syndrome) are described. In discussion of factors predisposing to appearance of such idiopathic calcifications, particular attention was given to meningoencephalitis suffered in childhood and coexistence of a tumour of the sella of prolactinoma type, in case 1. Attention was also called to progressive, copious clinical and radiological symptology of the discussed cases. It was impossible to suggest a probable type of inheritance (parents of the patients were dead). 相似文献
54.
Dorszewska J Adamczewska-Goncerzewicz Z Zukiel R Nowak S Moczko J 《Neurologia i neurochirurgia polska》2000,34(2):321-327
Changes in the content and composition of lipids in brain tumours of different degree of malignancy are still the subject of numerous scientific studies. It is known that in developing brain tumours structural and functional changes of its cells, take place, in which lipids play a crucial role. The examination of the lipid spectrum was conducted in a material extracted from tumour adjacent areas (by means of fenestration) as well as from tumours themselves in 11 patients (mean age 56.8 yrs). Based on histological studies all the tumours were qualified as glioblastoma 4th degree of malignancy. Lipids were isolated from the tumours as well as from their adjacent areas. Later on they were separated, using column chromatography and thin-layer chromatography, into three classes: phospholipids, galactolipids and neutral lipids. Separated lipids were subjected to quantitative analysis by spectrophotocolorimetric method. In comparison to adjacent areas, in tumours distinct changes of lipid levels were noticed in all analysed lipid classes. Statistical analysis showed significant decrease of phospholipids (elements stabilizing cell membranes) in tumours in comparison to their adjacent areas (Wilcoxon's test: p < 0.05). At the same time in tumours an increase of level of plasmalogens took place: phosphatidylcholine (PC) (PPC), phosphatidylethanolamine (PE) (PPE) typical elements of malignant tumours, responsible for cross cell membrane transportation processes. This phenomenon was accompanied by changes of levels of PC/PE and PC/SM (sphingomyelin) ratios connected with adhesiveness and other membrane features. Changes in the level of lipids, and phospholipids in particular, in glioblastoma 4th degree of malignancy in comparison to adjacent areas can indicate the pathological processes in cells of these tumours. 相似文献
55.
Infections by hepatotropic viruses belong to the most common complications of chemotherapy in children suffering from neoplastic
diseases. The rate of hepatitis B virus (HBV) or hepatitis C virus (HCV) infection and the effectiveness of passive immunization
against HBV were studied in 285 children; 148/285 with lymphoproliferative diseases and 137/285 with solid tumours. HBV infection
was observed in 10.2% children receiving hepatitis B immune globulin as compared to 36.8% without passive immunization against
HBV. Anti-HCV antibodies were similar in both groups amounting 38.7% and 32.6% respectively.
Conclusion The results show that hepatitis B immune globulin administration is effective and that HCV might become the main cause of
hepatitis among immunosuppressed patients in the future.
Received: 13 December 1994 / Accepted: 18 October 1996 相似文献
56.
Objective: To identify factors that influence a woman's decision to breast-feed.
Methodology: Five hundred and fifty-six women were recruited from the maternity wards of two Perth hospitals. Data were collected from a self-administered questionnaire completed by participants prior to discharge. Logistic regression analysis was used to determine factors influencing the initiation of breast-feeding.
Results: At discharge from hospital 83.8% of women were breast-feeding, including 6% who were giving complementary formula feeds. After controlling for potentially confounding demographic and biomedical factors, the father's reported preference for breast-feeding was found to be the most important factor influencing a woman's decision to breast-feed (OR 10.18).
Conclusion: Fathers participate in and influence the choice of infant feeding method and should be included in breast-feeding discussions. 相似文献
Methodology: Five hundred and fifty-six women were recruited from the maternity wards of two Perth hospitals. Data were collected from a self-administered questionnaire completed by participants prior to discharge. Logistic regression analysis was used to determine factors influencing the initiation of breast-feeding.
Results: At discharge from hospital 83.8% of women were breast-feeding, including 6% who were giving complementary formula feeds. After controlling for potentially confounding demographic and biomedical factors, the father's reported preference for breast-feeding was found to be the most important factor influencing a woman's decision to breast-feed (OR 10.18).
Conclusion: Fathers participate in and influence the choice of infant feeding method and should be included in breast-feeding discussions. 相似文献
57.
OBJECTIVE: Most neonatologists include an apnea-free period in the criteria for the discharge of preterm infants. However, the length of time one should wait after the cessation of apnea before sending an infant home without a monitor is debated. We undertook this study in an attempt to define a minimal and safe observation period between the time of the last apnea episode and discharge. METHODS: We reasoned that in infants with idiopathic apnea of prematurity, the intervals between days on which apnea occurs gradually increase until some point at which clinically significant apnea ceases. Therefore, knowledge about the intervals between days on which apnea occurred just before the last apnea would provide a reasonable estimate of the minimal safe observation interval between the last apnea and discharge. We reviewed the charts of 266 infants born in 1993 and 1994 at =32 weeks' gestational age or weighing =1500 g at birth from two institutions to determine the intervals between the day on which the last apnea occurred and the previous two days on which apnea occurred. One hundred seventy-five infants were excluded because they never experienced apnea, or data about the last apnea was missing, or they were on xanthines during the period encompassing the last 3 apnea days, or they weighed <1500 g or were <34 weeks' postmenstrual age at the time of the last apnea. Of the 91 remaining infants, gestational age at birth, birth weight, 1- and 5-minute Apgar scores, and discharge weight were not different between the two institutions. For each infant we determined the longest of the intervals between the 2 days on which apnea occurred previous to the day of the last apnea (MAXINT for maximum interval). The infants were then ordered by MAXINT and, starting at the longest MAXINT, the medical records of each infant were carefully examined for other conditions known to be associated with apnea (eg, recovering from anesthesia, sepsis, chronic lung disease, and so forth). The minimal safe observation period was then defined as the longest MAXINT in which there was at least 1 infant with no other explanation for the apnea other than prematurity. RESULTS: The median duration of the intervals between the 2 days on which apnea occurred previous to the day on which the last apnea occurred were 3. 0 and 2.0 days and the median duration of the MAXINT was 4.0 days. On careful examination of the charts, it was determined that each of 13 infants with a MAXINT preceding the day on which the last apnea occurred of greater than 8 days had some other condition that might result in apnea, including residual lung disease, sepsis, surgery, and so forth. In contrast, among the group of infants with a MAXINT of =8 days, at least 1 infant at each MAXINT (eg, 1 to 8) had significant apnea with no other explanation other than prematurity. CONCLUSIONS: We conclude that otherwise healthy preterm infants continue to have apneas separated by as many as 8 days before the last apnea before discharge. Conversely, infants with longer apnea intervals often have identifiable risk factors other than apnea of prematurity. 相似文献
58.
59.
Arif JM; Gairola CG; Glauert HP; Kelloff GJ; Lubet RA; Gupta RC 《Carcinogenesis》1998,19(8):1515-1517
The present study investigated the effects of dietary oltipraz on cigarette
smoke-related lipophilic DNA adduct formation. Female Sprague- Dawley rats
were exposed daily to sidestream cigarette smoke in a whole- body exposure
chamber 6 h/day for 4 consecutive weeks. One group of rats was maintained
on control diet while another group received the same diet supplemented
with either a low (167 p.p.m.) or high (500 p.p.m.) dose of oltipraz,
starting 1 week prior to initiation of smoke exposure until the end of the
experiment. Analysis of lipophilic DNA adducts by the nuclease P1-mediated
32P-post-labeling showed up to five smoke-related adducts. Adduct no. 5
predominated in both the lung and the heart while adduct nos 3 and 2
predominated in the trachea and bladder, respectively. Quantitative
analysis revealed that the total adduct level was the highest in lungs
(270+/-68 adducts/10(10) nucleotides), followed by trachea (196+/-48
adducts/10(10) nucleotides), heart (141+/-22 adducts/10(10) nucleotides)
and bladder (85+/-16 adducts/10(10) nucleotides). High dose oltipraz
treatment reduced the adduct levels in lungs and bladder by >60%, while
the reduction in lungs in the low-dose group was approximately 35%. In
trachea, the effect of low and high dietary oltipraz on smoke DNA adduction
was equivocal, while smoke-related DNA adducts in the heart were minimally
inhibited by high-dose oltipraz. In a repeat experiment that employed a
3-fold lower dose of cigarette smoke, oltipraz (500 p.p.m.) was found to
inhibit the formation of DNA adducts in rat lungs and trachea by 80 and
65%, respectively. These data clearly demonstrate a high efficacy of
oltipraz in inhibiting the formation of cigarette smoke-induced DNA adducts
in the target tissues.
相似文献
60.
Simone Boehrer Daniel Nowak Natasa Kukoc-Zivojnov Simone Hochmuth Soo-Zin Kim Dieter Hoelzer Paris S Mitrou Eckhart Weidmann Kai Uwe Chow 《Pharmacological research》2005,51(4):367-374
BACKGROUND: The role of Daxx, in particular its ability to promote or hinder apoptosis, still remains controversial. In order to elucidate the functional relevance of Daxx in the extrinsic signaling of malignant lymphocytes Jurkat T-cells were stably transfected with a Daxx-expressing vector or with the respective Daxx-negative control vector. RESULTS: Assessing first the impact of Daxx expression on the rate of proliferation we demonstrate that overexpression of Daxx alone is not sufficient to alter proliferation in neoplastic lymphocytes. Nevertheless, expression of Daxx down-regulates anti-apoptotic Bcl-2 and up-regulates pro-apoptotic BID. In addition, Daxx-overexpressing Jurkat cells exhibit a decreased expression of the pro-caspase-8, -10, -9 and -3 and a concomitant increase of the inhibitors of apoptosis proteins survivin, XIAP, cIAP-1 and -2. We further demonstrate, that upon incubation with various chemotherapeutic agents these Daxx-induced molecular alterations sensitize Jurkat T-cells to the apoptosis-inducing effects of specific chemotherapeutic agents. CONCLUSIONS: We here outline the molecular changes elicited by Daxx on major components of the apoptotic cascade of malignant lymphocytes and demonstrate the capacity of Daxx to sensitize these cells to the apoptosis-inducing effect of various chemotherapeutic agents. 相似文献