2023第六届中国大学生5分钟科研演讲（英语）大赛

作品标题（Title）

样本1

The effects of red and blue   light on alertness and mood at night

This study was designed to explore the roles that long- and   short-wavelength lights have on

momentary mood and alertness at night. Twenty-two subjects   participated in a mixed-design

experiment, where we measured the impact of two levels   of long-and-short-wavelength lights on

brain activity and on self-assessments of alertness,   sleepiness and mood. Measurements were

obtained 60 minutes prior to, during and after light   exposure. Results   showed that the red and the

blue lights increased electro  encephalographic beta power (12–30 Hz),   reduced sleepiness, and

increased positive affect relative to the previous   dim-light period indicating that alertness and

mood can be affected by light without necessarily   stimulating the melatonin pathway. The impact

of light was modest, however, compared to the increase   in fatigue over the course of the night.

样本2

The relationship between sleep and wake habits and academic performance   in medical students: a cross-sectional study

Background: The relationship between   the sleep/wake habits and the academic performance of medical students is   insufficiently addressed in the literature. This study aimed to assess the   relationship between sleep habits and sleep duration with academic   performance in medical students.

Methods: This study was conducted   between December 2009 and January 2010 at the College of Medicine, King Saud   University, and included a systematic random sample of healthy medical students   in the first (L1), second (L2) and third (L3) academic levels. A   self-administered questionnaire was distributed to assess demographics,   sleep/wake schedule, sleep habits, and sleep duration. Daytime sleepiness was   evaluated using the Epworth Sleepiness Scale (ESS). School performance was   stratified as “excellent” (GPA ≥3.75/5) or “average” (GPA <3.75/5).

Results: The final analysis   included 410 students (males: 67%). One hundred fifteen students (28%) had   “excellent” performance, and 295 students (72%) had “average” performance.   The “average” group had a higher ESS score and a higher percentage of   students who felt sleepy during class. In contrast, the “excellent” group had   an earlier bedtime and increased TST during weekdays. Subjective feeling of obtaining   sufficient sleep and non-smoking were the only independent predictors of   “excellent” performance.

Conclusion: Decreased nocturnal sleep time, late bedtimes during   weekdays and weekends and increased daytime sleepiness are negatively   associated with academic performance in medical students.

Influence of Genetically Modified Soya on the Birth-Weight and Survival   of Rat Pups

  Irina V .   Ermakova

ABSTRACT

Investigation of the   influence of GM soya on the birthrate and survival of the offspring of Wistar   rats were performed. A   group of female rats were fed GM soya flour before mating and pregnancy. The   control group of females were fed traditional soya and the third group of   females ,the positive control group, received feed without any soya. The   weight and the mortality rate of the newborn pups were analyzed. The study showed that there was a very high rate of pup   mortality(55.6%) in the GM soya group in comparison with the control group   and the positive control group (9% and 6.8% respectively). Moreover, death in   the first group continued during lactation, and the weights of the survivors   are lower those from the other two groups. It was revealed in these   experiments, that GM soya could have a negative influence on the offsprings   of Wistar rats

INTRODUCTION

It is well accepted by   scientists worldwide that four main sources of the hazards of genetically   modified organisms (GMO): 1) those due to the new genes, and gene products   introduced; 2) unintended effects inherent to the technology; 3) interactions   between foreign genes and host genes; and 4) those arising from the spread of   the introduced genes by ordinary cross-pollination as well as by horizontal   gene transfer (World Scientists' Statement 2000).

To understand what effect   they can have on us and on our animals and whether their risks may outweigh   the benefits it is vitally important to study the influence of these GM   plants in different organisms for several generations. The hazard of GMO was   shown for animals in extensive investigations (Traavik 1995; Ho and Tappeser   1997; Pusztai 1999 and 2001; Kuznetcov et al. 2004 and others). Earlier it   was shown that consumption of GM food by animals led to the negative changes   in their organisms. Experiments, conducted by Pusztai showed that potatoes   modified by the insertion of the gene of the snowdrop lectin (an insecticidal   proteins), stunted the growth of rats, significantly affected some of their   vital organs, including the kidneys, thymus, gastrocnemius muscle and others   (1998) and damaged their intestines and their immune system (Ewen and Pusztai   1999). Similar effect of GM potatoes on rats was obtained at the Institute of   Nutrition in Russia (Ermakova 2005). In another research of   Shubbert et al. (1998), foreign DNA, orally ingested by pregnant mice, was   discovered in blood (leukocytes), spleen, liver, heart, brain, testes and   other organs of foetuses and newborn animals. They   considered that maternally ingested foreign DNA could be potential mutagens   for the developing fetus. However, Brake and Evenson (2004) analyzing   the testis in mice as a sensitive biomonitor of potential toxic, didn’t find   adverse effects of transgenic soybean diet on fetal   development. From the literature review, there seems a lack of   investigations on the influence of GM crops on mammals, especially on their   reproductive function. Therefore, the objective of the study we undertake is   to see the effect of the most commonly used GM crop on the birth rate,   mortality and weight gain of rat pups, whose mother were fed diets   supplemented with Roundup-Ready soya, a kind of GM food.

METHODS

Animals:

Wistar rats were used as the   subjects in the experiment. The animals were brought up to sexual maturity on   laboratory rat feed. When their weight reached about 180 - 200 g, the female   rats were divided into 3 groups, housed in groups(3 rat/cage), and kept under   normal laboratory conditions. The feeding scheme was as follows. Females in   every cage daily received dry pellets from a special container placed on the   top of their cage. Those rats receiving soya flour supplement, were given the   soya flour in a small container placed inside their cage (20g x 40 ml water)   for three rats and, so 5 - 7g flour for each rat every day.

Experiment:

One group of female rats of   180 - 200 g weight was allocated to the experimental group, and received 5-7   soy a flour/rat/day prepared from Roundup-Ready soya, added to the rat feed   for two weeks. Another group females(3) were allocated to the control group,   but their diet was supplemented with the same amount of soya flour, prepared   from the traditional soya in which only traces (0.08+ 0.04%) of the GM   construct was present, most likely resulting from cross-contamination. We   also introduced a positive control group (in two cages:3x3), which had not   been exposed to soya flour. Therefore females only got the standard   laboratory feed without any supplementation, although it is acknowledged that   the energy and protein content of this diet was less than in the other two   groups.

After two weeks on the diets   all groups of 3 females were mated with two healthy males of the same age, which   had never been exposed to soya flour supplements. In order to avoid infection   of females, the sperm count and quality had not been determined. We carried   on feeding the respective diets to all females during mating and pregnancy.   Upon delivery, all females were transferred to individual cages, and the   amount of soya supplement was increased by an additional g for every pup   born. Lab feed and water was available for all animals during the   experimental period. When the rat pups opened their eyes and could feed   themselves (from 13-14 days of age), the daily dose of soya supplement was   increased till 2 - 3g for every pup, although all rats had free approach to   the soya. All rats ate their soya portions well. After the experiment was   finished the organs of some pups were taken out and weighed. The level of   mortality was analyzed by the one-way ANOVA, using the Newman-Keuls test for   share distribution. The pup’s weight and its distribution were checked by   Mann-Whitney test and Chi-square in StatSoft Statistica v6.0 Multilingua   (Russia).

RESULTS

By the end of the experiment,   from the 15 females included in the experiment, 11 gave birth and produced a   total of 132 rat pups. The 4 rats who became pregnant from 6 females on the   positive control diet gave birth to 44 pups (an average of 11 pups/female),   while the four females, from the six on GM soya flour supplemented groups   gave birth to 45 (11 .3 pups/female), and 3 from traditional soya group-33   pups (11 pups/mother).

Supplementation of the diet   of the females with GM soya led to the death of 25 pups, out of the 45 born   by the end of the third week of lactation, while during the same period on   the traditional soya supplemented diets only 3 pups died from 33. The   mortality in the positive control group was also 3, but from the larger   number of pups born, as seen in Table 1. High pup mortality was generally   characteristic for females fed the GM soya flour(Table2). Among the pups from   the females fed the positive control diet, 2 pups died during the first week,   and 1 during the second week after delivery. All pups from females fed   traditional soya flour died during the first week after birth. However, pups   from females fed the GM soya flour supplemented diet kept dying during   lactation period as it is evident from Table 3.

Table   1Mortality   of rat pups by the end of the 3rd week of lactation; compared to the GM soya   flour supplemented group

Table 2 Number rat pups died   from the litter of individual females on the GM soya flour supplemented diet

In two weeks after their   birth the weight of pups from the GM soya supplemented group was less (23.95g   ±1.5 g) than that of the pups of the positive control group (30.03g±1.1 g;   p<0.005), or from the traditional soya flour supplemented group (27.1 g±   0.9 g; p< 0.1). Since the number of surviving pups was so different, the   weigh distribution of the pups was compared in Table 4. From the data it is   evident that 36% of the pups from the GM soya group weighed less than 20 g,   in comparison with 6% in the positive control group, and with 6.7% found in   the traditional soya supplemented diet group (Table 4). The study of pup’s   organs mass showed that the organs of small pups from GM group were tiny in   comparison with the same of other groups except the brain mass (Table 5).   This fact indicated that the pups from the GM group were the same age as   others, but changes occurred with the development of internal organs. Slight   negative effect was found in the group which received the traditional soya,   but this effect was not significant. No mortality of females and survived   young pups eating the GM soya flour supplemented diet was observed.

DISCUSSION

The reproductive behaviour   of female rats fed on standard laboratory feed supplemented with soya flour   prepared from either genetically modified soya or traditional soya was   studied to see the effect of the diet on pregnancy, lactation and the growth   of the rat pups. Upon delivery, very unexpectedly a very high rate of pup   mortality (55.6%) was observed in the group of females whose diet was   supplemented with the GM soya flour in comparison with the pups of both the   positive control (6.8 %) and the traditional soya flour supplemented (9%)   groups. Also, in this group the pups continued to die over the period of   lactation, which occurred only in the GM soya fed group. At the same time,   the weights of the surviving rat pups were also lower. It is the more   surprising, since the pups were smaller, about half, therefore more milk   should have been available for the individual pups. They should have a better   chance to grow optimally, unless the amount, and/or the quality of the milk   were not affected by consuming the GM soya flour.

Our data allow us to   speculate and presume that the negative effect of GM soya on the newborn pups   could be explained by two possible factors. Firstly, it can be the result of   transformation, and insertion of the foreign genes, which could penetrate   into the sexual/stem cells, or/and into cells of the fetus, as it was   observed by Schubbert et al. (1998). Secondly, the negative effect could be   caused by the accumulation of Roundup residues in GM soya. However, no   mortality was observed with female rats, nor with the young pups survived,   although they also began to eat the GM soya. It is supposed that the effect   could be caused by the first factor. (2005)

References

Brake   D.G. and Evenson D.P.(2004): A generational   study of glyphosate-tolerant soybeans on mouse fetal,

postnatal,   pubertal and adult testicular development. Food Chemistry and Toxicology 42:   29-36.

Ewen SW,   Pusztai A (1999): Effect of diets containing genetically modified potatoes  expressing Galanthus  

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Ho MW and   Tappeser B (1997): Potential contributions of horizontal gene transfer to  the transboundary  

movement of   living modified organisms resulting from modern biotechnology. In   Transboundary Movement of Living Modified Organisms Resulting from Modern   Biotechnology: Issues and Opportunities for Policy-

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Schubbert R,   Hohiweg U, Renz D and Doerfier W (1998): On the fate of orally ingested  foreign DNA in mice: chromosomal association   and placental transmission in the fetus. Molecules. Genes and Genetics 259:   569-576.

Traavik T   (1999): Too Early May Be Too Late. Ecological Risks Associated with the Use of   Naked DNA as a  

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