The effect of the nature of the iron sources on the growth of different Corynebacterium diphtheriae strains

In the study of the influence of organic and inorganic sources of iron on the growth of 5 C. diphtheriae clinical isolates bacterial growth was found to depended on the nature of the source of iron and its concentration. Differences between the strains in the level of growth, observed when ferric sulfate was used as the only source of iron in the medium, were established. Quantitative differences in the concentrations of inorganic and organic sources of iron, necessary for growth, were determined. The influence of three chemical chelators on the growth of C. diphtheriae under the conditions of iron deficiency in the culture medium was studied. The results of the study are indicative of the possibility of the differentiation of C. diphtheriae isolated according to the level of iron consumption.     

Studies on the Anther Culture of Triticale

The present paper deals with the study of factors affecting the frequency of induction of Triticale pollen callus in anther culture. The following experimental results have been obtained: 1. The N6 medium and B5 medium were superior to MS medium in the production of pollen callus, and the difference between N6 medium and B5 medium was not obvious. 2. When 6 to 12 per cent of sucrose was added in medium, the induction frequency of pollen callus was higher, however, this higher frequency decreased with the concentration of sucrose down to 3 per cent. 3. It was found that there was no regultr correlation between the frequency of the formation of the pollen callus and concentrations of 2,4-D (0.5 ppm, 2 ppm, 5 ppm and 10 ppm) in medium. 4. Induction frequency of pollen callus increased apparently when active carbon (0.5 per cent) was added. 5. The liquid medium was capable of improving yields of the pollen callus. 6. It is not important for the formation of the pollen callus whether the cultures were kept in light or in dark. 7. Before inoculation the spikes were inserted into a bottle with N6 medium solution and pretreated at 3–5℃ for 3 days, the frequency of callus formation may be efficiently increased in comparison with those treated in water. When N6 medium was supplemented with 2,4-D (2 ppm), NAA (2 ppm) and kinetin (0.5 ppm), either used singly or in combination, the frequency of callus formation was not obviously increased.     

佤族的体质特征

调查了442例(男258例,女184例)佤族人的67项(观察项目9项,测量项目58项)体质人类学指标,计算了31项体质指数值,统计了部分指数的分型情况。研究结果显示:佤族人内眦褶率低(16.1%),上眼睑皱褶率高(96.8%),鼻根高度、鼻翼高度与上唇皮肤部高度均为中等型,耳垂多为圆型(58.1%),发色多为黑色,眼色多为褐色,肤色多为黄色。身高均数男为160.4cm,女为150.7cm,男女均为亚中等身材。体重均数男为54.9kg女为49.1kg。按指数分型标准,男女均以圆头型、高头型、阔头型、狭面型、狭鼻型、长躯干型、中腿型、中胸型出现率最高。此外,男性以宽肩型、中骨盆型出现率最高;女性的中肩型、窄骨盆型出现率最高。对包括佤族在内的我国32个人群(南、北方各16个人群)13项体质指标值主成分分析,结果显示佤族人身材矮小、纤瘦,面部及五官高度值较大,头长值较小,头面部及五官宽度值较大。佤族人具有蒙古人种南亚类型的体质特征。本文对佤族人体质特征形成的原因进行了初步分析。     

Sporulation in Bacillus subtilis. Effect of medium on the form of chromosome replication and on initiation to sporulation in Bacillus subtilis

Thymine-requiring mutants of Bacillus subtilis and mutants that are temperature-sensitive for initiation of chromosome replication have been used to study the relationship between sporulation and chromosome formation. The DNA synthesis that normally occurs when cells are transferred to sporulation medium is essential for spore induction. This is shown by the fact that thymine-starved cells are unable to form spores and are unable to perform even the earlier steps of sporulation, such as septum formation or synthesis of alkaline phosphatase. The nature of the medium in which the cells are growing while the DNA is being completed is also important because it determines both the shape and the position of the daughter chromosomes. If the cells are in a rich medium, the newly synthesized chromosomes are discrete and compact bodies: the cells are primed for growth, and sporulation cannot be induced by transferring them at this stage to a spore-inducing medium. If DNA synthesis was completed with the cells in a poor medium the daughter chromosomes, by the time DNA synthesis has ceased, are spread in a single filamentous band and the cells are morphologically already in stage I of sporulation.     

Effect of selected factors on the effectiveness ofCapsicum annuum L. anther culture

The primary aim of the study was to establish the effectiveness of induced androgenesis in in vitro anther culture of two pepper (Capsicum annuum L.) breeding lines--ATZ1 and PO, and a hybrid between these two lines (ATZ1 x PO)F1. Anther culture was maintained according to the method developed by Dumas de Vaulx et al. (1981) with some modifications. The experiment revealed that the effectiveness of androgenesis ranged from 4 %; for the ATZ1 line to 1.5 %; for the (ATZ1 x PO)F1 and strongly depended on the developmental stage of flower buds, as well as the conditions for anther culture maintenance. The development of androgenic embryos was successfully induced only in anthers which originated from the flower buds with petals equal or slightly longer than sepals and there was a clear relationship between the length of the period of anther induction on CP medium and the level of kinetin in R1 regeneration medium.     

The impact of culture medium on the development and physiology of biofilms of Pseudomonas fluorescens formed on polyurethane paint

Microbial biofilms cause the deterioration of polymeric coatings such as polyurethanes (PUs). In many cases, microbes have been shown to use the PU as a nutrient source. The interaction between biofilms and nutritive substrata is complex, since both the medium and the substratum can provide nutrients that affect biofilm formation and biodeterioration. Historically, studies of PU biodeterioration have monitored the planktonic cells in the medium surrounding the material, not the biofilm. This study monitored planktonic and biofilm cell counts, and biofilm morphology, in long-term growth experiments conducted with Pseudomonas fluorescens under different nutrient conditions. Nutrients affected planktonic and biofilm cell numbers differently, and neither was representative of the system as a whole. Microscopic examination of the biofilm revealed the presence of intracellular storage granules in biofilms grown in M9 but not yeast extract salts medium. These granules are indicative of nutrient limitation and/or entry into stationary phase, which may impact the biodegradative capability of the biofilm.     

Evaluation of Chromocult coliform agar for the detection and enumeration of Enterobacteriaceae from faecal samples from healthy subjects

The purpose of this study was to examine the use of Chromocult agar medium for isolation and enumeration of Enterobacteriaceae from human faecal samples, to compare it to MacConkey agar and to evaluate its usefulness as a possible alternative selective medium in human faecal studies. The medium was shown to be effective in identifying Escherichia coli and coliforms in faeces without the need for extensive accompanying biochemical tests for confirmation of identity. A positive correlation (r=0.86) was found between the recovery of Enterobacteriaceae on the two media, and no significant difference (P>0.05) between overall mean bacterial counts for the whole study group or at different intervals of faecal collection were observed. Chromocult agar is an effective replacement for MacConkey agar in human faecal studies and has the advantage of differentiating E. coli from other coliforms.     

中国克木人的体质特征

本文调查了我国克木人285例(男为141例,女为144例)的体质特征,计算出9项观察项目的出现率,58项测量项目的均数和标准差、31项指数值和分型情况,并与我国31个群体的体质特征进行了比较,得出我国克木人的体质特征为:蒙古褶出现率低,男为31.21%,女为32.64%;上眼睑皱褶出现率高,男为90.33%,女为93.75%;鼻根高度中等型出现率最高,男为65.96%,女为47.22%;鼻翼高度多为中等;耳垂多为三角型;上唇皮肤部高度多为中等型;发色多为黑色;眼色多为褐色;肤色多为黄色;圆头型、高头型、阔头型、狭鼻型、中躯干型、中胸型出现率最高;男性狭面型、亚长腿型、宽肩型、中骨盆型出现率最高;女性的阔面型、中腿型、中肩型、宽骨盆型出现率最高;男性身高均数为160.2cm,女身高均数为151.5cm,属亚中等身材;克木人男性与女性均具有生活在我国南方的人群的体质特征。     

On the mechanism of nitrate uptake by plant roots

Summary A study has been made on the influx and outflux of nitrogen compounds by the excised roots of barley, wheat and peas. A two way movement of nitrogen compounds was found to occur between root and external medium. Factors such as initial N content in the roots, species of plant and external concentration of N highly affect the extent to which this two-way movement proceeds. Further investigations are needed for more understanding of the nitrogen balance between plant roots and external medium.     

野生蔬菜鸭儿芹组织培养的初步研究

以野生鸭儿芹嫩芽为材料,利用MS培养基为基本培养基,添加不同种类和浓度的外源激素,对鸭儿芹的组织培养进行了初步研究.结果表明,诱导侧芽分化的最佳培养基为MS+6-BA 1.0 mg/L +NAA 1.0 mg/L;愈伤组织的继代培养基为MS+6-BA 1.0 mg/L+NAA 0.1 mg/L,添加抗坏血酸(Vc) 1.0 mg/L可以有效防止愈伤组织的褐化;鸭儿芹生根的最佳培养基为1/2 MS+IAA 1.0 mg/L.     

The role of iron in the production of hemolysin byListeria monocytogenes

The in vitro production of hemolysin byListeria monocytogenes, a facultative intracellular bacterial pathogen, was examined as a function of medium iron. There was an inverse relationship between iron and hemolysin production: Hemolysis increased as medium iron concentration decreased. This study offers the first evidence that the in vitro production of hemolysin byListeria monocytogenes is under the control of external iron in growth medium.     

In vitro growth and development of bovine oocyte-granulosa cell complexes on the flat substratum: effects of high polyvinylpyrrolidone concentration in culture medium

The aim of this study was to establish a culture system to support the growth of bovine oocytes as enclosed in granulosa cell complexes that extend on a flat substratum. Such systems have been established for mouse oocytes but are not applicable to larger animals because it is difficult to maintain an appropriate association between the oocyte and companion somatic cells. Growing bovine oocytes with a mean diameter of 95 microm were isolated from early antral follicles: the growing stage corresponds to that of oocytes in preantral follicles of 12-day-old mice. Oocyte-granulosa cell complexes were cultured for 14 days in modified TCM199 medium supplemented with 5% fetal bovine serum, 4 mM hypoxanthine, and 0.1 microg/ml estradiol. The novel modification made for this medium was a high concentration, 4% (w/v), of polyvinylpyrrolidone (PVP; molecular weight of 360000). The flat substratum used was either an insert membrane fit in the culture plate or the bottom surface of the wells of 96-well culture plates. PVP influenced the organization of complexes, resulting in a firm association between the oocyte and the innermost layer of surrounding cells. More oocytes enclosed by a complete cell layer were recovered from the medium supplemented with 4% PVP than from the control medium. Similarly, of the oocytes initially introduced into the growth culture, a significantly larger proportion developed to the blastocyst stage from medium containing 4% PVP than from medium without PVP. When PVP medium was used, the overall yield of blastocysts was similar between the system with the insert membranes (12%) and that with the 96-well culture plates (9%). A calf was produced from one of four embryos derived from oocytes grown in 96-well culture plates, matured, and fertilized in vitro and then transferred to a recipient cow.     

Evaluation of the influence of growth medium composition on cell elasticity

Recently, there has been an increasing interest in using the biomechanical properties of cells as biomarkers to discriminate between normal and cancerous cells. However, few investigators have considered the influence of the growth medium composition when evaluating the biomechanical properties of the normal and diseased cells. In this study, we investigated the variation in Young's modulus of non-malignant MCF10A and malignant MDA-MB-231 breast cells seeded in five different growth media under controlled experimental conditions. The average Young's modulus of MDA-MB-231 cells was significantly lower (p<0.0001) than the mean Young's modulus of MCF10A cells when compared in identical medium compositions. However, we found that growth medium composition affected the elasticity of MCF10A and MDA-MB-231 cells. The average Young's modulus of both cell lines decreased by 10-18% when the serum was reduced from 10% to 5% and upon addition of epidermal growth factor (EGF, 20 ng/ml) to the medium. Though these elasticity changes might have some biological impact, none was statistically significant. However, the elasticity of MCF10A was significantly more responsive than MDA-MB-231 cells to the medium composition supplemented with EGF, cholera toxin (CT), insulin (INS) and hydrocortisone (HC), which are recommended for routine cultivation of MCF10A cells (M5). MCF10A cells were significantly softer (p<0.002) when grown in medium M5 compared to a standard MDA-MB-231 medium (M1). The investigation of the effects of culture medium composition on the elastic properties of cells highlights the need to take these effects into consideration when interpreting elasticity measurements in cells grown in different media.     

Effects of medium composition on the growth and lipid production of microplasmodia of Physarum polycephalum

Physarum polycephalum is a plasmodial slime mold. One of the trophic stages in the life cycle of this organism is a plasmodium. In submerged culture, plasmodia are fragmented into microplasmodia. The latter both lack cell walls and are capable of rapid growth. There has been limited information on the effects of medium composition on the growth and lipid accumulation of microplasmodia. In this study, optimization of medium components by response surface methodology showed that tryptone and yeast extract concentrations had the most significant effects on lipid and biomass production; significant synergistic interactions between glucose and tryptone concentration on these responses were also recorded. The optimal medium was composed of 20 g/L of glucose, 6.59 g/L of tryptone, and 3.0 g/L of yeast extract. This medium yielded 13.86 g/L of dry biomass and 1.97 g/L of lipids. These amounts are threefold higher than those of the American Type Culture Collection (ATCC) medium. In addition, biomass and lipid production reached maximal values between only 4 and 5 days. Fatty acid compositions analysis by gas chromatography-mass spectrometer (GC–MS) revealed that P. polycephalum lipids consisted mainly of oleic acid (40.5%), linoleic acid (10%), and octadecynoic (15.8%). This is the first report on the fatty acid composition of P. polycephalum microplasmodia. These results suggest that the biomass of microplasmodia could be used as a source of material for direct conversion into biodiesel because of the absence of cell walls or it could also be used as a supplemental source of beneficial fatty acids for humans, albeit with some further evaluation needed.     

大豆体细胞胚胎发生影响因素的研究

研究了影响大豆幼胚培养体细胞胚胎发生频率的9个因素。诱导体细胞胚胎发生的适宜幼胚长度为4mm;随着供体植株发育阶段的提高诱导频率下降;最适基本培养基为MS培养基; 蔗糖浓度从1.5％提高到9％,诱导频率逐渐下降;过高的维生素B1浓度对胚胎发生不利;2,4 — D的诱导效果优于NAA,适宜的2,4—D浓度为20ppm; 光、暗处理与生长素种类和浓度之间存在交互作用,接种方式对诱导频率影响很大,体细胞胚只在下表皮与培养基接触的幼子叶的上表皮上产生,当上表皮与培养基接触时,两个表皮都不能产生体细胞胚;被试的所有基因型都能被诱导胚胎发生,不同基因型的诱导频率存在差异。     

Initial observations on the effect of medium composition on the differentiation of murine embryonic stem cells to alveolar type II cells

The pluripotency and high proliferative index of embryonic stem (ES) cells make them a good potential source of cells for tissue engineering purposes. We have shown that ES cells can be induced to differentiate in vitro into pulmonary epithelial cells (type II pneumocytes) using a serum-free medium designed for the maintenance of mature distal lung epithelial cells in culture (SAGM). However, the resulting cell cultures were heterogeneous. Our aim in this study was to attempt to increase pneumocyte yield and differentiation state by determining which medium components enhance the differentiation of pneumocytes and modifying the medium accordingly. Quantitative RT-PCR was used to measure changes in the expression of a type II pneumocyte-specific gene, surfactant protein C (SPC), in response to alterations in the cell culture medium. Results suggested that most individual SAGM growth factors were inhibitory for type II pneumocyte differentiation, with the largest increases in SPC expression (approximately threefold) being observed upon removal of retinoic acid and triiodothryonine. However, large standard deviations occurred between replicates, illustrating the highly variable nature of ES cell differentiation. Nevertheless, these observations represent an initial step towards achieving directed differentiation of pneumocytes from stem cells that could lead to their purification for tissue engineering purposes.     

Effect of ganglionic stimulating and blocking agents on the fast components of colonic myoelectrical activity in the rat

The presence of two types of fast myoelectrical activities, medium fast activity and fast activity, has been demonstrated previously in the electromyogram of colon in normal children and in the rat by the authors. An absence of medium fast activity in Hirschsprung's disease and in experimental aganglionosis of colon in the rat has also been described. In the present study the fast components of colonic myoelectrical activity were analysed during the procedures affecting ganglionic transmission. It was observed that ganglionic stimulants, such as balloon inflation, and intra-arterial injections of acetylcholine and small amounts of nicotine, increased the spike activity and the frequency of medium fast activity without affecting fast activity. The intra-arterial injections of ganglionic blocking agents, such as nicotine in large amounts and pentolinium tartrate, completely abolished the medium fast activity. These observations suggest that the ganglionic activity is responsible for the genesis of medium fast activity and that the absence of cholinergic ganglionic transmission is the most important single factor for the reported altered electromyogram pattern in aganglionosis.     

Effect of the dielectric constant of the medium on the photooxidation of chlorophyll a by parabenzoquinone]

Spectrophotometric study was carried out of the effect of medium polarity on the parabenzoquinone photooxidation of chlorophyll "a" at lower temperature using as solvents toluene and CCl4 containing different quantities of polaric solvents, methanole, ethanole, amilic alkohol, acetone. It is shown that the photoreaction with the formation of primary photooxidized form of the pigment starts only if some amount of the polar component is in the medium. The data are in favour of the suggestion that chlorophyll and quinone in non-polar medium form an reaction complex which disintegrates under the given conditions at a definite value of medium polarity.