Influence of the culture medium on the expression of surface polypeptides of Yersinia enterocolitica

Three polypeptides (200, 46, and 25 kDal) encoded by the virulence plasmid were detected by SDS-PAGE in the outer membrane of Yersinia enterocolitica 09 grown at 37 degrees C in brain-heart infusion medium. Bacteria grown at the same temperature in the tissue culture medium RPMI 1640 expressed five additional polypeptides (170, 135, 118, 100, and 98 kDal), but the 25-kDal band was not seen. The protein profile in RPMI 1640 resembles the expression pattern displayed by yersiniae when grown in vivo. The immunoblot of total membrane proteins of bacteria grown in brain-heart infusion medium revealed eight plasmid-encoded polypeptides, four of which were also in the outer membrane preparations, including a 28-kDal polypeptide. These peptides do not coincide with known plasmid-encoded outer membrane proteins.     

Killer toxins of certain yeast strains have potential growth inhibitory activity on gram-positive pathogenic bacteria

The killer yeast strains which are encountered most frequently among species in the genera Saccharomyces, Candida, Hansenula, Pichia and Kluyveromyces (ten killer strains in toto) were tested for the activity of their toxins on the growth of some pathogenic bacteria (four Gram-positive and six Gram-negative strains) in a test in which purified toxins were not required. Neither toxins of the killer Saccharomyces cerevisiae and Pichia membranefaciens strains were active against the bacterial strains. In contrast the killer toxins of Hansenula anamola, Hansenula mrakii, Candida tropicalis, Kluyveromyces drosphilarum and Kluyveromyces lactis showed potential growth inhibitory effects on Gram-positive pathogenic bacteria. Thus, yeast killer toxins were found to be active only on Gram-positive bacterial cell types.     

Effect of culture medium on the in vitro secretion activity of prothoracic glands from Pseudaletia separata

BACKGROUND: Killer lymphocytes secrete perforin, a 67 kDa protein that initiates T-cell cytolysis following aggregation and pore formation in target membranes. The resulting pores cause a breakdown of the transmembrane osmotic gradient and allow other cytolytic mediators to enter the target cell and initiate apoptosis. The cytolytic domain resides within the first 34 residues of the amino terminus of perforin, with residues 1-19 being sufficient for cytolytic activity. RESULTS: The solution structure of a 22-residue synthetic peptide (P22), corresponding to the amino terminus of human perforin, has been determined using high resolution nuclear magnetic resonance spectroscopy in the presence and absence of perdeuterated detergent (SDS) micelles. In aqueous solution, P22 exists mainly in a random conformation. However, it adopts a hook-like structure at the carboxyl terminus in the presence of SDS micelles when the positively charged residues cluster to form a turn that provides a binding surface to the negatively charged sulfate headgroups. CONCLUSIONS: The strong electrostatic interaction between the cationic region of the P22 peptide and the lipid headgroups probably weakens the membrane, facilitating insertion of the relatively neutral/hydrophobic stretch of P22, and is representative of the initial step of the lytic pathway. The structural model described here is probably relevant to understanding the mechanisms of other cationic antimicrobial peptides.     

Characterization of the embryotrophic activity of exogenous protein-free oviduct-conditioned medium used in culture of cattle embryos

Bovine zygotes, obtained after in vitro maturation and fertilization of oocytes from slaughtered cow ovaries, were cultured in droplets of nonconditioned or conditioned medium on bovine oviduct cell monolayers. The media tested were Medium 199 alone and Medium 199 supplemented with 10% fetal calf serum (FCS). Oviduct conditioning increased both early cleavage and development to blastocysts. Only the effect on early cleavage was mimicked by FCS. The blastocysts obtained in serum-free conditioned medium (SFCM) appeared morphologically normal and had the same cell number as those produced in conditioned medium containing serum. Their hatching rates did not differ. Transfer of 16 blastocysts developed in SFCM to 16 synchronized recipients resulted in five pregnancies (31%), indicating good embryonal viability. Boiling of SFCM resulted in a total loss of activity, while heating at 56 degrees C for 30 min had no deleterious effect. A 10-kDa ultrafiltration of SFCM removed the blastocyst development-supporting activity from the filtrate but not the early cleavage-favoring activity. This allows us to conclude that at least two different factors are present in SFCM: one of low molecular mass (< approximately 10 kDa), needed to obtain the 5-8 cell stage and mimicked by FCS, and another of higher molecular mass allowing embryos to develop from the 8-cell to blastocyst stage.     

Influence of the medium on children's story apprehension.

Compared children's apprehensions of an unfamiliar story either read to them from an illustrated book or presented as a comparable televised film. 24 younger and 24 older children (mean ages 7.6 and 9.6 yrs, respectively) were randomly assigned to one medium condition and individually presented the story. Response measures examined recall of story content as well as inferences about characters and events. Ss exposed to the televised story remembered more story actions, offered estimates of shorter elapsed time and distance traveled for carrying out a repeated story event, and relied more on visual content as the basis for inferences. In comparison, Ss who were read the story in picture book form recalled more story vocabulary, based their inferences more on textual content, general knowledge, and personal experience, and made more use of the storytelling situation as an opportunity to ask questions and make comments about the story. To the extent that children have repeated experience with specific media, such differential medium effects on apprehension suggest important implications for children's cognitive development. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Changes in ribosomal activity of Escherichia coli cells during prolonged culture in sea salts medium

The activity of ribosomes from a clinical isolate of Escherichia coli, exposed to starvation for 7 days in sea salts medium, was investigated by measuring the kinetic parameters of ribosomal peptidyltransferase, by using the puromycin reaction as a model reaction. No alterations in the extent of peptide bond formation were observed during starvation. In contrast, a 50% reduction in the kmax/Ks ratio could be seen after 24 h of starvation; an additional 6 days of starvation resulted in a progressive but less abrupt decline in the kmax/Ks value. (kmax is the apparent catalytic rate constant of peptidyl transferase, and Ks is the dissociation constant of the encounter complex between acetyl (Ac)[3H]Phe-tRNA-poly(U)-ribosome and puromycin.) Although the distribution of ribosomal particles remained constant, a substantial decrease in the number of ribosomes per starved cell and a clear decline in the ability of ribosomes to bind AcPhe-tRNA were observed, particularly during the first day of starvation. Further analysis indicated that rRNA in general, but especially 23S rRNA, was rapidly degraded during the starvation period. In addition, the L12/L7 molar ratio decreased from 1.5 to 1 during the initial phase of starvation (up to 24 h) but remained constant during the subsequent starvation period. Ribosomes isolated from 24-h-starved cells, when artificially depleted of L7/L12 protein and reconstituted with L7/L12 protein from mid-logarithmic-phase cells, regenerated an L12/L7 molar ratio of 1.5 and restored the peptidyltransferase activity to a substantial level. An analogous effect of reconstitution on the efficiency of ribosomes in binding AcPhe-tRNA was evident not only during the initial phase but throughout the starvation period.     

Growth medium effect on the antifungal activity of LY 303366

The incidence of circumcision in 256 pregnant Nigerian Igbo women was 124 (48.4%). This incidence increased with increasing social class (circumcision index (C.I), 0.06 to 16.50, for social class 1 to 5); was least among the least age range, 16-20 years (C.I, 0.45); and among the primigravidae (C.I, 0.36) compared to the grandmultipara (C.I, 4.43) (P < 0.05.). Simple excision was the commonest type of circumcision, 122 (98.4%). The genital introitus was mildly scarred in 48 (38.7%) respondents, moderately scarred in 47 (37.9%) and severely scarred in 29 (23.4%). Ninety four (36.7%) of the respondents were not aware of their circumcision status, while 91 (96.8%) of the circumcised women had it performed during infancy. On the question of continued practice of female circumcision in their villages, 43 (16.8%) respondents replied, "yes"; 138 (53.9%), "no"; 25 (9.8%) "Sometimes"; and 50 (19.5%), "don't know". The incidence of episiotomy during delivery was similar for both circumcised, 47 (18.4%)and uncircumcised, 46 (18.0%) respondents (P = 0.05). More uncircumcised respondents, 31 (12.1%) were sexually satisfied during intercourse than the circumcised, 11 (4.3%) (P < 0.05). Of the 118 female offsprings of the respondents, 109 (92.4%) were not circumcised while 9 (7.6%) were. Increased public enlightenment on the risks of female circumcision is expected to eradicate the practice by the next generation     

Three-dimensional culture of hepatocytes in a continuously flowing medium

Rat hepatocytes were maintained on three-dimensional cultures on sponge discs kept in Spinner Baskets (New Brunswick Scientific Co., New Brunswick, NJ, USA) with continuously circulating serum-free hepatocyte growth medium (HGM) containing hepatocyte growth factor (HGF) and epidermal growth factor (EGF). Hepatocytes were embedded in polyester sponge discs with a collagen gel at the concentration of 5 million cells/ml. Atmospheric gas containing 7% CO2 was directly bubbled into the medium. Agitation by the impeller created a continuous medium-flow through the packed hepatocytes. Comparison between identically prepared perfused and stationery cultures showed that hepatocytes in the perfused cultures maintain higher levels of DNA synthesis. These results demonstrate the value of perfusion systems and also show that hepatocytes can proliferate and maintain differentiation in three-dimensional culture environments.     

Direct inhibitory effect of uremic toxins and polyamines on proliferation of VERO culture cells

Steroidogenic tumors are derived from cells of male and female reproductive tracts, adrenal glands, central nervous system, and, to a lesser degree, from the liver and pituitary gland. The symptoms caused by these tumors are related to their secretory products. Because enzymatic pathways are shared by both adrenal- and gonadal-derived tissues, and the conversion of some of these steroids occurs in the adipose tissue, positive identification of many lesions cannot be based on peripheral blood hormone levels alone, but require complex protocols to improve diagnostic accuracy. Furthermore, these tumors often are smaller than the size limit of conventional imaging modalities and thus demand more precise imaging techniques. Although diagnosis and localization may be challenging, the rewards of a positive prognosis, with complete reversal of symptoms, are more likely to occur with early detection and treatment. This article is a review of the clinical syndromes associated with pediatric steroidogenic tumors; suggested strategies to facilitate their diagnosis, localization, and treatment are provided.     

Fragile sites on human chromosomes: demonstration of their dependence on the type of tissue culture medium

The observation of heritable fragile sites on human chromosomes prepared for lymphocyte cultures has been shown to depend on the type of tissue culture medium in which the lymphocytes are grown. The sites are observed at a much greater frequency when medium 199 is used than when RPMI 1640, Ham's F10, Eagle's (basal), and CMRL 1969 are used. One site on the X chromosome is of clinical significance in that it is a marker for X-linked mental retardation.     

Effect of the age of the culture and the composition of the medium on alkaloid biosynthesis by Penicillium gorlenkoanum

The production of the alkaloids costaclavine and epicostaclavine by Penicillium gorlenkoanum was studied as a function of the culture age and the composition of the growth medium. The alkaloids were found in the mycelium and, in great quantities, in the cultural broth. The production of the extracellular alkaloids started from the first days of growth and run in parallel to the biomass accumulation; the synthesis of costaclavine and epicostaclavine was maximal at the end of the logarithmic-stationary growth phases. The medium supplied with mannitol, succinic acid and 1% KH2PO4 was optimal for epicostaclavine synthesis. A carbohydrate or organic acid substitution as well as a variation in the concentration of phosphate changed the proportion between epicostaclavine and costaclavine contents. The biosynthesis of epicostaclavine was inhibited almost entirely by the glucose deficiency (2%) in the medium. This glucose concentration, phosphate excess (10 g/l), and the presence of citric or tartaric acids created favourable conditions for costaclavine biosynthesis.     

Periodontal ligament cell culture on the hydrophobic substrate coated with proteins of periodontal ligament fibroblast-conditioned medium

In regenerating periodontal ligament (PDL) around the root of an artificial tooth, an important role is played by some physiologically active substance that promotes adhesion of the cells to the surface of the tooth root and induces cell proliferation and differentiation. In this study, the supernatant of the conditioned medium (CM) of dog periodontal ligament fibroblast (DPLF) was fractionated using an ion exchange chromatography-diethylaminoethyl (IEC-DEAE) column. DPLFs were cultured on hydrophobic dishes coated with each fraction. Cell proliferative activity and alkaline phosphatase (ALPase) activity, including electron microscopic features of the contact surface between the cells and the dish, were investigated. The DPLF-CM was separated by IEC-DEAE column into six fractions. Each fraction promoted an increase in DNA content and ALPase activity of the cultured DPLF, and especially remarkable were fractions 2 and 3. Fraction 2 at a molecular weight (Mw) of 210, 160, 85, 50 and 22 kD, and fraction 3 at Mw = 21 and 23 kD contained the type of proteins not found in other fractions. Electron microscopic analysis revealed that the cells in the coating group were in close contact with the surface of the dishes and that fine fibers protruding from the cell membrane clinged to the dishes. In the control group, a wide gap between the cells and the dishes was observed. These findings suggest that the DPLF-CM fractions contain specific physiological activating factors that induce proliferation and differentiation as well as cell adhesion of the DPLF cells.     

Influence of medium tonicity on respiration by suspensions of human platelets

We describe the use of graded decrements of medium osmolarity to progressively unmask respiratory capacities of whole human platelets in suspension. This departure led to the first demonstration that human platelet mitochondria are capable of tightly coupled respiration that responds to addition of mitochondrial substrates, ADP, and inhibitors in a way that other mammalian mitochondria are expected to behave. In 300 mosM media added alpha-glycerophosphate (G3P), succinate, or ADP effected only slight stimulation of base-line O2 consumption. At 180 mosM O2 consumption peaked and was not significantly affected by succinate or ADP. At 80 mosM base-line O2 consumption fell precipitously and was restored by G3P or succinate prior to being raised to its highest levels by ADP. Added NADH had no effect on O2 consumption at 80 mosM but sharply stimulated it when platelet suspensions were exposed to 60 mosM media by pretreatment with distilled water. At 80 mosM, selected compounds that inhibit or uncouple oxidative phosphorylation of isolated mammalian mitochondria from a variety of cells exerted similar influences on while platelets.     

Influence of the nutrient medium on the total lipid fatty acid composition of Actinomyces canosus

GLC was used to study the composition of endocellular fatty acids of Actinomyces canosus 89 grown on a chemically defined medium and on a complex medium to which various components were added. Total lipids of the culture contain saturated and unsaturated fatty acids, from C13 to C18, with one or two double bonds. Addition of components to the medium stimulated the biosynthesis of myristic, stearic, oleic, and linoleic fatty acids. Changes in the composition of the growth medium modify the ratio between saturated and unsaturated fatty acids of total lipids, increasing the content of unsaturated fatty acids due to a higher rate of synthesis of linoleic and oleic fatty acids. An increase in the content of unsaturated fatty acids is a positive factor because these acids are involved in important physiological functions of both this organism and other living organisms.     

Gaze-related activity of putative inhibitory burst neurons in the head-free cat

1. Previous studies in the cat have demonstrated that output neurons of the superior collicular as well as brain stem omnipause neurons have discharges that are best correlated, not with the trajectory of the eye in the head but, with the trajectory of the visual axis in space (gaze = eye-in-head + head-in-space) during rapid orienting coordinated eye and head movements. In this study, we describe the gaze-related activity of cat premotor "inhibitory burst neurons" (IBNs) identified on the basis of their position relative to the abducens nucleus. 2. The firing behavior of IBNs was studied during 1) saccades made with the head stationary, 2) active orienting combined eye-head gaze shifts, and 3) passive movements of the head on the body. IBN discharges were well correlated with the duration and amplitude of saccades made when the head was stationary. In both head-free paradigms, the behavior of cat IBNs differed from that of previously described primate "saccade bursters". The duration of their burst was better correlated with gaze than saccade duration, and the total number of spikes in a burst was well correlated with gaze amplitude and generally poorly correlated with saccade amplitude. The behavior of cat IBNs also differed from that of previously described primate "gaze bursters". The slope of the relationship between the total number of spikes and gaze amplitude observed during head-free gaze shifts was significantly lower than that observed during head-fixed saccades. 3. These studies suggest that cat IBNs do not fit into the categories of gaze-bursters or saccade-bursters that have been described in primate studies.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of market factors on the pricing of exchange traded metals in the medium term

On the basis of comparison of the influence of the stock exchange factors on the pricing of nonferrous metals for medium term with similar results for short term, it has been established that the main attention should be paid to the changes in the pricing environment on the metal market as a function of the prices of exchange traded metals. The situation on the market of energy carriers (hydrocarbons) and the European, American, and Asian stock exchanges can be based on parity and even significantly influence the variation of the metal prices. In the medium term, constructive development of metal trade should be reasonably promoted by changing the elasticity of supply with regard to prices for exchange traded metals and by applying the stock exchange factors that positively influence the pricing on commodity and stock markets.     

An EGF receptor-mediated signal attenuates the inhibitory effect of LPA on an adenylate cyclase activity

A tyrosine kinase receptor-mediated and a heterotrimeric G protein-coupled receptor-mediated signals have been shown to evoke distinct intracellular signaling events. There has been increasing evidence that cross-talk exists between a tyrosine kinase receptor-mediated and a heterotrimeric G protein-coupled receptor-mediated signal transduction pathways. In the present study, we have studied effects of EGF receptor activation on activities of inhibitory G protein (Gi). We show that the amounts of Gi/Go ADP-ribosylated by islet-activating protein (IAP) increased by 30-40% in the membranes of Rat 1 fibroblast cells pretreated with EGF compared with those without pretreatment. When an effect of lysophosphatidic acid (LPA) stimulation on an adenylate cyclase activity was examined, LPA partly attenuated forskolin-stimulated adenylate cyclase activity via Gi because IAP pretreatment blocked the inhibitory effect of LPA. Pretreatment with EGF reduced the ability of LPA to inhibit the forskolin-stimulated adenylate cyclase activity, while the pretreatment did not have any effects on the forskolin-stimulated activity. Thus, the EGF receptor-mediated signal appears to cause the impairment of Gi function in Rat 1 fibroblast cells.     

希腊、罗马文化对英语词汇的影响

介绍希腊、罗马神话的起源、发展及其相互关系,采用典型范畴理论,划分出源于希腊罗马神话的习语及由专有名词转化而来的普通名词,揭示其中一些较为典型词语的来源及其文化内涵,并阐述其对英语语言产生的影响,最后指出语言学习者应探索文化背景知识,尤其应探索和积累古希腊、罗马文化知识。