scholarly journals Some observations on the influence of the micro-environment on loss of M substance in strains of Streptococcus pyogenes

1956 ◽  
Vol 54 (1) ◽  
pp. 89-98
Author(s):  
P. J. Wormald
Keyword(s):  
Streptococcus Pyogenes ◽  
Growth Rates ◽  
Liquid Media ◽  
Naturally Occurring ◽  
Nutrient Value ◽  
Type 3 ◽  
Selection Of ◽  
Apparently Healthy

1. An M-producing strain of Streptococcus pyogenes type-12 was shown to be carried on the surface of apparently healthy tonsils for at least 3 years.2. Loss of M substance in a strain of type-3 in a tonsillar carrier was shown to be by gradual replacement of matt forms by glossy variants. This pair of naturally occurring variants showed very different growth rates as mixtures in liquid media.3. Under suitable conditions, glossy variants regularly appeared and replaced the M-producing strain from which they were derived in these and all other strains of type-3 and type-12 tested from a wide variety of sources.4. It is suggested that the selection of variants by the differential nutrient value of the micro-environment is the deciding factor in carrier strains showing loss of M substance.

Optimization of the selection of analysis methods for the determination of naturally occurring radionuclides

Kerntechnik ◽  
2008 ◽  
Vol 73 (3) ◽  
pp. 118-121
Author(s):  
T. Heinrich ◽  
L. Funke ◽  
M. Köhler ◽  
U.-K. Schkade ◽  
F. Ullrich ◽  
...  
Keyword(s):  
Naturally Occurring ◽  
Analysis Methods ◽  
Naturally Occurring Radionuclides ◽  
Selection Of

scholarly journals Changes in genetic constitution and sterol composition during growth of nystatin-resistant heterokaryons ofNeurospora crassa

1983 ◽  
Vol 42 (1) ◽  
pp. 91-103 ◽  
Author(s):  
Jill E. Ogden ◽  
Morris Grindle
Keyword(s):  
Growth Rates ◽  
Minimal Medium ◽  
Resistant Mutant ◽  
Sterol Composition ◽  
Sensitive Strain ◽  
Genetic Constitution ◽  
Polyene Antibiotic ◽  
Ofneurospora Crassa ◽  
Synthetic Media ◽  
Selection Of

SUMMARYHeterokaryons ofN. crassawere synthesized from homokaryotic strains differing in sterol composition and sensitivity to the polyene antibiotic nystatin. Mycelia of the nystatin-sensitive strainerg-1+contained ergosterol and episterol, and the nystatin-resistant mutanterg-1 contained fecosterol and lichesterol. Mycelia of heterokaryons with different proportions oferg-1+:erg-1 nuclei contained various proportions of the four sterols. Ergosterol was the principal sterol in heterokaryons with more than 5%erg-1+nuclei.Heterokaryons with various proportions oferg-1+:erg-1 nuclei were grown for several weeks along tubes of synthetic media. Growth rates were stable on minimal medium and nutritionally supplemented media but nuclear proportions often fluctuated. Growth rates fell sharply on nystatin-supplemented media and there were adaptive increases in proportions of mutanterg-1 nuclei which resulted in selection of nystatin-resistant homokaryotic mycelia.

scholarly journals IMPLEMENTING HOME SAFETY TOOLKIT TO CAREGIVERS OF VETERANS WITH DEMENTIA

2019 ◽  
Vol 3 (Supplement_1) ◽  
pp. S243-S243
Author(s):  
Scott A Trudeau
Keyword(s):  
Formative Evaluation ◽  
Veterans Health ◽  
Health Administration ◽  
Home Safety ◽  
Structured Interviews ◽  
Potential Benefits ◽  
Facilitators And Barriers ◽  
Key Staff ◽  
Type 3 ◽  
Selection Of

Abstract The purpose of this project was to study the processes necessary to make a Home Safety Toolkit (HST) for Veterans with dementia accessible to veterans and their caregivers. This Type 3 Implementation–Effectiveness Hybrid Research Design, included diagnostic analyses of the current processes by which Veterans receive home safety items, and identification of modifications necessary in order to provide the HST to Veterans with dementia. Two Veterans Health Administration Networks, one in the Northeast and one in the Mid-Atlantic region, participated. A formative evaluation used semi-structured interviews with key staff informants and caregivers identified facilitators and barriers to successful acquisition and use of home safety items. Qualitative data analysis reveals key barriers of time and cost, selection of best items, and caregiver reluctance to change. There was resounding support from caregivers regarding the potential benefits of self-paced toolkit including education and home safety items to implement for their veteran.

scholarly journals Coriolis effects on the elliptical instability in cylindrical and spherical rotating containers

2007 ◽  
Vol 585 ◽  
pp. 323-342 ◽  
Author(s):  
M. LE BARS ◽  
S. LE DIZÈS ◽  
P. LE GAL
Keyword(s):  
Growth Rates ◽  
Close Agreement ◽  
Unstable Mode ◽  
Quantitative Agreement ◽  
Fixed Rate ◽  
Elliptical Instability ◽  
Normal Mode Theory ◽  
Set Up ◽  
First Time ◽  
Selection Of

The effects of the Coriolis force on the elliptical instability are studied experimentally in cylindrical and spherical rotating containers placed on a table rotating at a fixed rate $\tilde{\Omega}^G$. For a given set-up, changing the ratio ΩG of global rotation $\tilde{\Omega}^G$ to flow rotation $\tilde{\Omega}^F$ leads to the selection of various unstable modes due to the presence of resonance bands, in close agreement with the normal-mode theory. No instability occurs when ΩG varies between −3/2 and −1/2 typically. On decreasing ΩG toward −1/2, resonance bands are first discretized for ΩG<0 and progressively overlap for −1/2 ≪ ΩG < 0. Simultaneously, the growth rates and wavenumbers of the prevalent stationary unstable mode significantly increase, in quantitative agreement with the viscous short-wavelength analysis. New complex resonances have been observed for the first time for the sphere, in addition to the standard spin-over. We argue that these results have significant implications in geo- and astrophysical contexts.

scholarly journals Growth and Flowering of ‘Alice du Pont’ Mandevilla in Response to Sumagic

1992 ◽  
Vol 10 (1) ◽  
pp. 36-39
Author(s):  
C. Frederick Deneke ◽  
Gary J. Keever ◽  
John A. McGuire
Keyword(s):  
Growth Rates ◽  
Vegetative Growth ◽  
Foliar Application ◽  
Application Rate ◽  
Single Application ◽  
Flower Diameter ◽  
Selection Of

Abstract Vegetative growth of ‘Alice du Pont’ mandevilla can be controlled by selection of an appropriate foliar application rate of Sumagic (uniconazole) and application interval. A single application of 5 to 20 ppm ai Sumagic (uniconazole) controlled vegetative growth for only 3 to 4 weeks; after this time, growth rates were similar to control plants. Multiple applications of 5 to 20 ppm ai Sumagic (uniconazole) effectively restricted vegetative growth; as the concentration of Sumagic (uniconazole) increased, the interval between applications increased from about 4 (5 ppm) to 6 (20 ppm) weeks. A single application of higher rates (30 to 120 ppm) of Sumagic (uniconazole) was phytotoxic. Generally, time to flowering increased and flower diameter decreased when application rate increased.

scholarly journals Genetic marker studies of poliovirus: II. Strains isolated from cases of poliomyelitis associated with the administration of live attenuated vaccine

1967 ◽  
Vol 65 (1) ◽  
pp. 77-84 ◽  
Author(s):  
Yvonne E. Cossart
Keyword(s):  
Oral Vaccine ◽  
Paralytic Poliomyelitis ◽  
Live Attenuated Vaccine ◽  
Naturally Occurring ◽  
South Wales ◽  
Vaccine Type ◽  
Marker Studies ◽  
Type 3

Strains of poliovirus were obtained from 13 of the 18 persons in England and Wales with paralytic episodes after administration of oral vaccine in 1962. They have been studied using three marker tests: the R.C.T.40 test, intratypic serodifferentiation and inhibition by dextran sulphate. For comparison a number of strains from subjects with non-paralytic vaccine-associated reactions and from patients with paralytic poliomyelitis not related to vaccine were also tested.Of the eight patients excreting type 1 strains seven came from South Wales where an outbreak was in progress. They all resemble naturally occurring strains from the outbreak in growing at 39·3° but not at 39·8° C.Only one subject excreted type 2 virus which was of vaccine type.The type 3 strains included a series from a family group where a range of results from vaccine to the wild range was obtained. Three other patients with vaccineassociated paralysis excreted type 3 strains with the characteristic of naturally occurring strains.

scholarly journals A Naturally Occurring Rgg Variant in Serotype M3 Streptococcus pyogenes Does Not Activate speB Expression Due to Altered Specificity of DNA Binding

2009 ◽  
Vol 77 (12) ◽  
pp. 5411-5417 ◽  
Author(s):  
Kyle V. Kappeler ◽  
Srivishnupriya Anbalagan ◽  
Alexander V. Dmitriev ◽  
Emily J. McDowell ◽  
Melody N. Neely ◽  
...  
Keyword(s):  
Amino Acid ◽  
Streptococcus Pyogenes ◽  
Murine Model ◽  
Cysteine Protease ◽  
Phenotypic Diversity ◽  
Transcriptional Regulator ◽  
Amino Acid Position ◽  
Invasive Disease ◽  
Naturally Occurring

ABSTRACT The transcriptional regulator Rgg of Streptococcus pyogenes is essential for expression of the secreted cysteine protease SpeB. Although all isolates of S. pyogenes possess the speB gene, not all of them produce the protein in vitro. In a murine model of infection, the absence of SpeB production is associated with invasive disease. We speculated that naturally occurring mutations in rgg, which would also abrogate SpeB production, may be present in invasive isolates of S. pyogenes. Examination of the inferred Rgg sequences available in public databases revealed that the rgg gene in strain MGAS315 (a serotype M3 strain associated with invasive disease) encodes a proline at amino acid position 103 (Rgg103P); in contrast, all other strains encode a serine at this position (Rgg103S). A caseinolytic assay and Western blotting indicated that strain MGAS315 does not produce SpeB in vitro. Gene-swapping experiments showed that the rgg gene of MGAS315 is solely responsible for the lack of SpeB expression. In contrast to Rgg103S, Rgg103P does not bind to the speB promoter in gel shift assays, which correlates with a lack of speB expression. Despite its inability to activate speB expression, Rgg103P retains the ability to bind to DNA upstream of norA and to influence its expression. Overall, this study illustrates how variation at the rgg locus may contribute to the phenotypic diversity of S. pyogenes.

Genetic engineering of crop plants: from genome to gene

1997 ◽  
Vol 33 (01) ◽  
pp. 15-33 ◽  
Author(s):  
B. P. Forster ◽  
M. A. Lee ◽  
U. Lundqvist ◽  
S. Millam ◽  
K. Vamling ◽  
...  
Keyword(s):  
Genetic Engineering ◽  
Plant Breeding ◽  
Crop Plants ◽  
Trade Routes ◽  
The Past ◽  
Naturally Occurring ◽  
New Ideas ◽  
New Varieties ◽  
Transitional Phase ◽  
Selection Of

Genetic engineering of crop plants has been in progress since the dawn of agriculture, about 10 000 years ago. For millennia the genetic make-up of our crop plants has been changed by mankind's selection of naturally occurring variants. As the trade routes were developed, novel plant types were introduced into new environments and provided more variation from which to choose. At the end of the nineteenth century an understanding of the laws of heredity was gained and plant breeding protocols were devised whereby selection became accompanied by deliberate crossing. As the knowledge of the genetic structure of crop plants improved, new ways of manipulation were invented and exploited. Indeed plant breeding became a testing bed for new ideas in genetics. For the plant breeder the techniques which were most widely employed in the past were those which aided breeding, for example techniques which speeded up the production of new varieties, but still used traditional routes of crossing and selection. This was a transitional phase between plant breeding as an art and plant breeding as a science.

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