Factors affecting the frequency of concealed heterokaryosis in Saccharomyces cerevisiae

In this work, studies on the phenomenon of concealed heterokaryosis that we previously detected in the saccharomycetes yeast strains were continued. New approaches to high effectiveness of isolation of cytoductants carrying the concealed nucleus were implemented, and the composition of individual concealed heterokaryons, zygotic clones, and the first zygotic buds was analyzed by a micromanipulator. The relationship between a delay in the growth of the parental strain (a potential donor of the concealed nucleus) and a decline in the frequency of the appearance of concealed heterokaryons (HKC) was observed. It is assumed that different replication rates of two nuclei of the heterokaryon probably underlie the appearance of HKC. A drastically decreased level of replication of one of the parental nuclei may be connected with the fact that binuclear buds appear extremely rarely and give rise to the rapidly "purified" progeny consisting of cells carrying the second nucleus with normal replication. A lack of the phenotype allows rare binuclear cells to persist as concealed heterokaryons. HKC may be detected only when cells of either parental type are isolated on the corresponding selective media.     

Factors affecting postural stability of healthy young adults

The objective of this paper was to examine the relationship between body balancing functions and body characteristics, motor abilities and reaction time. Subjects were 33 university students and 11 professional basketball players sorted into four groups of athletic and non-athletic women and men. Each group consisted of eleven subjects. The body height, weight was measured and the body mass index (BMI) calculated. A bioelectrical device computed the body fat (%). Static and dynamic motor tests, as well as static and dynamic balance tests were used. The reaction time (RT) to sound and light stimuli was measured. The regression analysis of the data revealed significant linear relationship between the amplitude of body sways (BS) and BMI in all groups. Also high correlation was found between back muscle strength and BS in all groups except the non-athletic women. Negative correlation was found between endurance capacity and BS in basketball players, i.e. at higher endurance capacity smaller amplitude BS occurred (r = -0.620, p < 0.04). The RT values showed significant correlations with BS only in the basketball players (r = 0.620, p < 0.04). It is concluded that increase in BMI, back muscle strength and endurance capacity is associated with better postural stability. Some motor abilities (hip flexibility, vertical jumping) show no significant correlations with body balancing, while other motor performances (static hanging) and RT values correlate well with BS only in the well-trained elite basketball players.     

Factors affecting the frequency and pattern of mitomycin C-induced chromatid exchanges

Data are reported on the frequency and pattern of Mitomycin C-induced exchanges in lymphocytes of a marsupial hybrid Macropus rufogriseus × Wallabia bicolor and in four individuals, two male and two female, of M. rufogriseus. In the hybrid, exchanges are found almost exclusively between the M. rufogriseus chromosomes and the breakpoints are in the C-banded pericentromeric regions. In the four M. rufogriseus animals the data show no evidence for preferential exchanges between homologues and so provide no justification for postulating somatic pairing between homologues. Comparisons of the frequency of exchanges between non-homologous chromosomes in the hybrid and in the four individuals of M. rufogriseus show that there is no difference in the frequency of exchange for any given chromosome but that the specific pattern of exchanges may differ between animals. The data are interpreted as providing evidence for different types of heterochromatin and possible bases for these differences are discussed.     

Increased frequency of micronuclei in B and T8 lymphocytes from smokers

The frequency of micronuclei was measured in peripheral B lymphocytes and some T lymphocyte subpopulations from 5 medium-tar cigarette smokers, and 5 non-smokers with no regular exposure to tobacco smoke. The peripheral lymphocytes were stimulated in vitro with phytohemagglutinin and B lymphocytes and the various T lymphocyte subsets were classified by a recently developed MAC (Morphology, Antibody, Chromosomes) method which allows the immunologic identification of different cell lineages. An increased frequency of micronuclei was observed in B and especially in the suppressor/cytotoxic T8 lymphocytes from smokers, as compared with non-smoker values. In non-smoker cultures, no differences in the frequency of micronuclei were observed among the different T lymphocyte subsets. In these cultures, B cells tended to have a higher frequency of micronuclei than did T cells. The proportions of B cells and the various T subpopulations among mitotic and interphasic lymphocytes from smokers and non-smokers were also determined. The proportions of B cells and T cell subsets among all mitotic lymphocytes were similar in smokers and non-smokers. Contrarily, a significant decrease in the proportion of T8 lymphocytes among all interphasic lymphocytes was observed in cultures derived from smokers.     

Enhancement of micronuclei frequency in the Tradescantia/micronuclei test using a long recovery time

The Tradescantia/micronuclei test (TRAD/MCN) is a well-validated test for monitoring environmental genotoxicants. These pollutants induce at the early meiotic stage of pollen mother cells chromosome fragments which become micronuclei at the tetrad stage. The standard test protocol requires some hours of exposure of the inflorescences and a recovery time of about 24 hours to reach the early tetrad stage. Since the recovery period represents a critical step of the TRAD/MCN, experiments were performed to establish its length in plants of clone #4430 of the hybrid T. hirsutiflora x T. subacaulis which is widely used in environmental monitoring. The aim of the present research was to ascertain the exact duration of recovery time in order to improve the sensitivity of the TRAD/MCN test. First, studies were performed to select the flowers at the beginning of the meiosis, and then anthers were sampled and studied for a period of 48-86 hours. The complete meiosis in the plants examined required about 80 hours. Second, exposure to genotoxic substances followed by different recovery times was carried out to demonstrate that effectiveness of the TRAD/MCN test is closely related to the duration of the recovery time. The test was carried out by exposing inflorescences to known mutagens (sodium azide and maleic hydrazide) for six hours followed by different recovery times (24-72 hours). The results showed that the frequency of micronuclei in the pollen mother cells increased with the length of the recovery time.     

Factors affecting ciliary beat frequency in the intrapulmonary airways of rats.

The influence of drugs on ciliary beat frequency in the intrapulmonary airways of rats was studied in vitro. Sympathomimetic drugs significantly increased the ciliary beat frequency. Acetylcholine, pilocarpine, aminophylline, prednisolone, potassium iodide, and ammonium chloride also caused cilioexcitation, though to a lesser degree. Phentolamine, 5-hydroxytryptamine, histamine, and acetylcysteine caused an apparent cilioinhibition. However, histamine in high doses also caused an incoordination of ciliary beat. Codeine and phenobarbital were slightly cilioexcitatory in low concentrations and ciliodepressive at higher concentrations.     

影响油菜下胚轴外植体芽高频率再生的因素

以芥菜型油菜DB3 的下胚轴为外植体 ,分析了苗龄、激素、AgNO3 对油菜外植体的高频率再生的影响。结果发现 ,3～ 5d的苗用于诱导愈伤组织较佳 ,6 BA 1 .5mg/L +NAA 0 .1mg/L的组合对下胚轴芽的分化较好 ,AgNO3 可提高下胚轴芽的分化率     

Factors affecting recombinant frequency in protoplast fusions of Streptomyces coelicolor.

The optimum concentration of polyethylene glycol 1000 (PEG) for the production of recombinants through protoplast fusion in Streptomyces coelicolor was about 50% (w/v). The addition of 14% (v/v) dimethyl sulphoxide to the fusion mixture enhanced recombination frequencies, but only at sub-optimal PEG concentrations. After treatment of protoplasts with 50% PEG for 1 min, the frequency of recombinants in a multi-factor 'cross' sometimes exceeded 20% of the total progeny. The frequency of recombinants in the progeny could be significantly enhanced by ultraviolet irradiation of the parental protoplast suspensions immediately before fusion.     

Factors affecting the excision frequency of the maize transposable element Ds in Arabidopsis thaliana

A two-element transposon system based on the maize elements Ac and Ds is currently being used for insertional mutagenesis in Arabidopsis. With the aim of making this system as efficient as possible we have continued to analyse several parameters which affect Ds activity in Arabidopsis. The influence of genomic position on Ds excision has been analysed in five lines carrying Ds integrated in different genomic locations. Differences in both somatic and germinal excision were observed between the different lines. The relationship between somatic and germinal excision, the timing of excision events and environmental influences on transposition frequency have been investigated. The effect of varying dosage of the different elements was also analysed. A strong positive dosage effect was observed for the transposase source, but not for the Ds element. Analysis of germinal excision events showed that the majority of them occurred very late in the development of the plant, resulting in the majority of Ds transpositions being independent events.     

Factors affecting transfer frequency of pAM beta 1 from Streptococcus faecalis to Lactobacillus plantarum.

Conjugal transfer of streptococcal plasmid pAM beta 1 to Lactobacillus plantarum by a filter mating method was examined under various conditions. The transfer frequency depended greatly on the type, pore size, and side (front or back) of the membrane filter. The passage of sterilized water through the membrane under reduced pressure after donor and recipient cells were trapped on it increased the transfer frequency about 10-fold.     

Factors affecting the occurrence of postpartum prolonged luteal activity in clinically healthy high-producing dairy cows

The objective was to characterize risk factors affecting the occurrence of prolonged luteal phase (PLP) in postpartum, clinically healthy, high-producing dairy cows. Transrectal ultrasound examinations of the reproductive tract were performed twice weekly, from the 1st to 8th wk after calving in 151 multiparous clinically healthy lactating Holstein cows (mean ± SD of peak milk yield = 56.7 ± 7.4 kg). Serum samples were collected twice weekly to measure progesterone and every 2 wk to detect β-hydroxybutyrate (βHB), and α1-acid glycoprotein (AGP). Body condition score (BCS) was recorded weekly after calving. Based on the serum progesterone profile, 52 (34.4%) cows had normal ovarian activity (NLA), whereas 36 (23.8%) cows had a prolonged luteal phase (PLP), the most prevalent type of abnormal pattern of luteal activity. Furthermore, 63 cows with short luteal activity, delayed first ovulation, or cystic ovaries were excluded from this study. Serum AGP concentrations, as an indication of postpartum chronic endometritis, were not different (P > 0.05) between cows with NLA and PLP. Categories of peak milk yields (kg) were positively correlated with the incidence (%) of cows with PLP (r = 0.87, P = 0.02). Furthermore, milk yield peak, day of milk yield peak, mean milk yield (8 wk in milk), and milk yield on the expected day of luteolysis were higher (P < 0.05) in cows with PLP than NLA, and cows with PLP had greater loss of BCS (P = 0.007) than those with NLA. The likelihood of cows with PLP decreased by 0.9-fold for every 1 d delay of commencement of luteal activity (C-LA). Moreover, the likelihood of cows with PLP increased by 1.8-fold for each 1 mmol/L increase in the 1st wk serum βHB concentrations. In conclusion, higher mean of milk yield, greater BCS loss, earlier C-LA, and later peak milk yield were the major risk factors affecting the occurrence of postpartum PLP in clinically healthy, high-producing dairy cows.     

Ozone-induced micronuclei frequency in rat alveolar Type II cells

The effect of ozone, a ubiquitous air pollutant, was tested on cultured pulmonary epithelial type II cells isolated from rats. After 40-hour culture, the cells were exposed for 6 h to 400 ppb of ozone or air. The number of micronucleated cells was counted after the exposure. In each group, 17000 cells were evaluated. The number of micronucleated cells was significantly increased in the ozone-exposed group (12.24 per 1000 cells) compared to the control group (5.00 per 1000 cells). The results showed the mutagenic effect of ozone exposure on alveolar type II cells, manifested in the increased frequency of their micronuclei.     

Factors affecting the frequency of tetraploid cells in a predominantly diploid suspension culture ofDaucus carota

Summary Tetraploid clones were isolated from a predominantly diploid culture line ofDaucus carota by plating alone or after colchicine treatment. Although individually these tetraploid clones had similar growth rates to the diploid culture, they were progressively eliminated from mixtures with the diploid line. As the diploid culture line always contained a low frequency of tetraploids, the selective elimination of tetraploids must have been balanced by their continuous production. The frequency of endoreduplication detected was too low to maintain the equilibrium frequency of tetraploids and it is proposed that polyploidisation also occurred by endomitosis. The mean frequency of tetraploid metaphases within the diploid culture line was reduced by shortening the interval between subcultures from 14 to 7 days. This 7-day regime also eliminated linear growth and stationary phase periods, but did not alter the maximum growth rate or mitotic index of the culture. It is argued that the change in mean tetraploid metaphase frequency is indicative of a change in the number of tetraploid cells within the culture, brought about by an alteration in the equilibrium between production and elimination of tetraploid cells.     

No increase in micronuclei frequency in cultured blood lymphocytes from a group of filling station attendants

Service station attendants are workers that are definitely exposed to petroleum derivatives. Taking into account that this exposure has been considered to possess genotoxic risk, here we present data on the biomonitoring of a group of 50 service station workers and 43 controls. Micronuclei (MN) from peripheral blood lymphocytes has been considered as the genetic endpoint to be studied and, in addition, data on the concentration of aromatic hydrocarbons at the workplace, urinary metabolites and differential white blood cell count have also been analysed. The results obtained indicate no significant differences between petrol station attendants and controls, when the effects of petrol exposure were investigated by differential white blood cell count and analysis of MN frequencies in phytohaemagglutinin-stimulated lymphocytes. Regarding the urinary metabolites, a significant increase in the phenol level was found in the exposed workers.     

Effect of smoking habit on the frequency of micronuclei in human lymphocytes: results from the Human MicroNucleus project

The effect of tobacco smoking on the frequency of micronuclei (MN) in human lymphocytes has been the object of many population studies. In most reports, the results were unexpectedly negative, and in many instances smokers had lower frequencies of MN than non-smokers. A pooled re-analysis of 24 databases from the HUMN international collaborative project has been performed with the aim of understanding the impact of smoking habits on MN frequency. The complete database included 5710 subjects, with 3501 non-smokers, 1409 current smokers, and 800 former smokers, among subjects in occupational and environmental surveys. The overall result of the re-analysis confirmed the small decrease of MN frequencies in current smokers (frequency ratio (FR) = 0.97, 95% confidence interval (CI) = 0.93-1.01) and in former smokers (FR = 0.96, 95% CI = 0.91-1.01), when compared to non-smokers. MN frequency was not influenced by the number of cigarettes smoked per day among subjects occupationally exposed to genotoxic agents, whereas a typical U-shaped curve is observed for non-exposed smokers, showing a significant increase of MN frequency in individuals smoking 30 cigarettes or more per day (FR = 1.59, 95% CI = 1.35-1.88). This analysis confirmed that smokers do not experience an overall increase in MN frequency, although when the interaction with occupational exposure is taken into account, heavy smokers were the only group showing a significant increase in genotoxic damage as measured by the micronucleus assay in lymphocytes. From these results some general recommendations for the design of biomonitoring studies involving smokers can be formulated. Quantitative data about smoking habit should always be collected because, in the absence of such data, the simple comparison of smokers versus non-smokers could be misleading. The sub-group of heavy smokers (> or =30 cigarettes per day) should be specifically evaluated whenever it is large enough to satisfy statistical requirements. The presence of an interaction between smoking habit and occupational exposure to genotoxic agents should be always tested.     

恶梦的影响因素研究

恶梦是与睡眠相关的常见心理现象.目前,恶梦的概念仍具有争议,但恶梦与心理健康的关系,已经引起了研究者广泛关注.恶梦的病因学研究表明,恶梦与遗传及生理因素有关;恶梦具有人格倾向性,应激与创伤因素是其产生的主要原因,与分裂症等精神疾病高度相关;恶梦与睡眠呼吸相关因素关系不是很明确;恶梦与多巴胺受体激动剂等药物显著相关,恶梦产生的其他因素研究尚待发现.然而这些因素与恶梦的因果关系并不确定,各因素之间的关系及作用机制有待进一步研究.未来的研究可以改进研究方法,扩大研究对象,进行纵向研究等.     

Higher frequency of dicentrics and micronuclei in peripheral blood lymphocytes of cancer patients

The presence of dicentric chromosome (DC) and micronuclei (MN) frequency in the peripheral blood lymphocytes of 25 cancer patients prior to chemo and radiotherapy and 21 healthy volunteers were studied. The overall DC and MN showed significantly higher frequency compared to those obtained in normal healthy volunteers (p<0.0001). However, among 25 patients only 15 showed a higher frequency of DC aberration, nine patients showed the presence of minutes (M) and seven patients showed chromatid breaks (ChB). The reasons for the higher frequency of aberration observed in these cancer patients are discussed in this paper.