利用转录调控因子Bas1p和Bas2p协同作用提高酿酒酵母cAMP产量的研究

【目的】研究转录调控因子Bas1p和Bas2p协同作用对重组酿酒酵母(Saccharomyces cerevisiae)胞外c AMP产生的影响,初步优化发酵培养基。【方法】通过共整合表达策略,在c AMP产生菌酿酒酵母G5中超表达Bas1p和Bas2p,摇瓶发酵实验考察了Bas1p和Bas2p协同作用对菌株生长及胞外c AMP产生的影响,进一步考察了酵母粉和蛋白胨含量及前体物腺嘌呤对菌株生长和c AMP产生的影响。【结果】超表达Bas1p和Bas2p使菌株在1×YP培养基中发酵120 h时的c AMP产量较出发菌株提高51.4%,达到2 253.8μmol/L;将1×YP中的酵母粉和蛋白胨含量翻倍(即2×YP培养基)发酵120 h时的c AMP产量提高至4 450.4μmol/L;在2×YP培养基中添加0.5 g/L浓度的腺嘌呤时,c AMP产量进一步提高至5 314.3μmol/L。【结论】强化Bas1p和Bas2p的协同作用及相应地优化培养基组分有助于酿酒酵母胞外c AMP生产。     

Radioiodine fallout and breast-feeding

The rationale for suspension of breast-feeding after exposure to radioiodine in fallout is presented.     

Mobile laboratory in Sierra Leone during outbreak of Ebola: practices and implications

<正>Dear Editors,Ebola virus disease(EVD)is an acute,serious and fatal illness caused by the Ebola virus.EVD was first identified in 1976 during two simultaneous outbreaks,one in Nzara,Sudan,and the other in Yambuku,Democratic Republic of Congo[1].The latter o ccurred in a village near the Ebola River,from which the disease takes its name.Since its     

Paradoxes, Problems, and Opportunities in Zaire

Zaire: The Cycle of the Serpent. 1992. 58 minutes, color. Directed by Thierry Michel. First Run/Icarus Films, 153 Waverly Place, New York, NY 10014. (212) 727-1711.
The Last Colonials. 1995. 61 minutes, color. Directed by Thierry Michel. First Run/Icarus Films, 153 Waverly Place, New York, NY 10014. (212) 727-1711.     

Prevention and treatment practices and implications for malaria control in Mukono District Uganda

Available data in Uganda indicate a resurgence of malaria morbidity and mortality countrywide. This study assessed the burden of malaria, treatment and prevention practices in order initiate a policy debate on the scaling-up of current interventions. A triangulation of methods using a cross-sectional survey and key informant interviews was used to assess self-reported malaria at a household level in Mukono District, Uganda. A total of 5583 households were surveyed, and a high proportion (2897, 51.9%) reported a person with malaria two weeks prior to the survey. Only 546 households (9.8%) owned and used insecticide-treated nets (ITNs) for malaria prevention. Similarly, only a few households (86, 1.5%) used indoor residual spraying. Self-treatment with home-stocked drugs was high, yet there was low awareness of the effectiveness of expired drugs on malaria treatment. Self-reported malaria was associated with socioeconomic, behavioural and environmental factors, but more especially with household ownership of ITNs. These results will contribute to the current debate on identifying new approaches for scaling-up prevention interventions and effective case management, as well as selection of priority interventions for malaria control in Uganda.     

Zaire butterflies and faunal diversity in the tropics

Samples of butterflies were collected along the Zaire River from its source to Kisangani and in the Ituri region. The number of species flying in the same area has been estimated wherever possible, and the degree of faunal similarity at different sites. The number of species increases as one proceeds north from 50–100 to 100–150, and the fauna is separable into two groups. The difference in faunal composition and diversity is related to the southern boundary of the rain forest. The comparative poorness of the butterfly fauna in tropical Africa compared to tropical South America is discussed, with reference to the parallel difference in the bird faunas of the two continents.     

Correlates of cytotoxic T-lymphocyte-mediated virus control: implications for immunosuppressive infections and their treatment

A very important question in immunology is to determine which factors decide whether an immune response can efficiently clear or control a viral infection, and under what circumstances we observe persistent viral replication and pathology. This paper summarizes how mathematical models help us gain new insights into these questions, and explores the relationship between antiviral therapy and long-term immunological control in human immunodeficiency virus (HIV) infection. We find that cytotoxic T lymphocyte (CTL) memory, defined as antigen-independent persistence of CTL precursors, is necessary for the CTL response to clear an infection. The presence of such a memory response is associated with the coexistence of many CTL clones directed against multiple epitopes. If CTL memory is inefficient, then persistent replication can be established. This outcome is associated with a narrow CTL response directed against only one or a few viral epitopes. If the virus replicates persistently, occurrence of pathology depends on the level of virus load at equilibrium, and this can be determined by the overall efficacy of the CTL response. Mathematical models suggest that controlled replication is reflected by a positive correlation between CTLs and virus load. On the other hand, uncontrolled viral replication results in higher loads and the absence of a correlation between CTLs and virus load. A negative correlation between CTLs and virus load indicates that the virus actively impairs immunity, as observed with HIV. Mathematical models and experimental data suggest that HIV persistence and pathology are caused by the absence of sufficient CTL memory. We show how mathematical models can help us devise therapy regimens that can restore CTL memory in HIV patients and result in long-term immunological control of the virus in the absence of life-long treatment.     

Wave-like spread of Ebola Zaire

In the past decade the Zaire strain of Ebola virus (ZEBOV) has emerged repeatedly into human populations in central Africa and caused massive die-offs of gorillas and chimpanzees. We tested the view that emergence events are independent and caused by ZEBOV variants that have been long resident at each locality. Phylogenetic analyses place the earliest known outbreak at Yambuku, Democratic Republic of Congo, very near to the root of the ZEBOV tree, suggesting that viruses causing all other known outbreaks evolved from a Yambuku-like virus after 1976. The tendency for earlier outbreaks to be directly ancestral to later outbreaks suggests that outbreaks are epidemiologically linked and may have occurred at the front of an advancing wave. While the ladder-like phylogenetic structure could also bear the signature of positive selection, our statistical power is too weak to reach a conclusion in this regard. Distances among outbreaks indicate a spread rate of about 50 km per year that remains consistent across spatial scales. Viral evolution is clocklike, and sequences show a high level of small-scale spatial structure. Genetic similarity decays with distance at roughly the same rate at all spatial scales. Our analyses suggest that ZEBOV has recently spread across the region rather than being long persistent at each outbreak locality. Controlling the impact of Ebola on wild apes and human populations may be more feasible than previously recognized.     

Locomotor behavior of Pan paniscus in Zaire

The locomotor behavior of Pan paniscus was studied over a four-week period in Equateur, Republic of Zaire. Bonobos were found to be both arboreal and terrestrial in their daily activities. In the trees adult bonobos are basically quadrupedal, but they also have significant components of armswinging, diving, leaping, and bipedalism in their locomotor repertoire.     

Prevalence and duration of breast-feeding in Manitoba.

The rate of breast-feeding in the first 3 months post partum was studied in a group of 456 mothers. At 3 months 58% had been or still were breast-feeding their infants. The mothers who breast-fed were older, had a higher level of education, had a higher socioeconomic status, and were more likely to live on farms or in small towns, to have attended prenatal education classes and to have previously breast-feds. There were no significant differences between the method of feeding and the sex or birthweight of the infant, the maternal weight/height ratio or the participation of the father in the prenatal education classes. At 1 month 45% of the infants, at 2 months 35% and at 3 months 28% were being breast-fed. Public programs to promote breast-feeding as normal, beneficial and satisfying to both mother and infant are necessary so that more mothers will attempt to breast-feed their infants. Support for continuance of breast-feeding is needed in the hospital as well as in the home and the community.     

Determinants of breast-feeding and post-partum amenorrhoea in Orissa

A life table analysis is made of the duration of breast-feeding and post-partum amenorrhoea in Orissa, India, taking one variable at a time using data from a baseline survey of fertility and mortality (BSFM) conducted on the lines of the World Fertility Survey. Then a multivariate (proportional hazard) analysis showed that socioeconomic factors including residence, caste status and education influence the breast-feeding and post-partum amenorrhoea periods. There was no effect of maternal age on the length of breast-feeding, but mean length of post-partum amenorrhoea varied with age. The durations of breast-feeding and post-partum amenorrhoea are strongly related.     

Estimation of births averted due to breast-feeding and increases in levels of contraception needed to substitute for breast-feeding

After contraceptive use, breast-feeding duration is the major determinant of the birth interval length. Three methods of estimating births averted by breast-feeding, and the increase in contraceptive use needed to substitute for breast-feeding, are presented. Method 1 simply utilizes Bongaarts' Ci, and the other two are based on mean birth intervals with and without breast-feeding. Estimates for each method are derived for six countries with DHS surveys from the mid-1990s: Burkina Faso, Uganda, India, Indonesia, Brazil and Peru. The estimated percentage of additional births that would occur if there were no breast-feeding ranged from 1-4%, in Brazil to about 50% in Burkina Faso and Uganda, reflecting very low breast-feeding in Brazil and very high levels in the sub-Saharan African nations. Strengths and limitations of the three methods are considered.     

Further decline of breast-feeding.

In a personal survey, by structured interview, we have investigated some of the factors which led 100 healthy mothers (63 primiparae) to decide to breast-feed their healthy babies, and 100 comparable mothers (43 primiparae) to decide to bottle-feed. Past experience (either personal or that of their family and friends) was of considerable but not overriding importance, and the decisions were apparently made surprisingly early in most cases. But much more effective educational approaches are needed, perhaps starting in the schools, and concentrated in the antenatal clinic, to allow mothers to reach the right decision for themselves and their babies. The reasons for early cessation of breast-feeding were also investigated, and suggested that those mothers opting for breast-feeding need better technical information and support.     

Increasing prevalence of breast-feeding.

Two studies were performed to gauge the prevalence of and attitudes towards breast-feeding. Mothers delivered in one month in 1975 and in one month in 1977 were sent a questionnaire one month later to determine whether they were breast-feeding their babies; those that were received a second questionnaire at three months. The prevalence of breast-feeding increased significantly between 1975 and 1977, and in both periods primiparas were more likely to breast-feed than multiparas. A survey of mothers'' intentions to breast-feed showed that there were no significant racial differences, but that 82% of women in social classes I and II intended to breast-feed compared with 54% in classes IV and V. These results show that, although the level of breast-feeding was high in 1975, a campaign directed at mothers, doctors, midwives, and health visitors did increase the prevalence of breast-feeding.