Detection of microgram quantities of carrier ampholytes in electrofocused proteins by thin-layer chromatography

A rapid and sensitive method for the detection of carrier ampholyte contamination in electrofocused proteins is described. Samples containing proteins and carrier ampholytes were applied to cellulose thin-layer chromatographic sheets and developed in 10% trichloroacetic acid. Proteins and large-molecular-weight carrier ampholytes were precipitated at the origin while 10% trichloroacetic acid-soluble carrier ampholytes migrated as a diffuse ninhydrin (nitrogen)-positive area at an R_f greater than 0.50. We found that 1.25 μg of carrier ampholytes contained enough 10% trichloroacetic acid-soluble components to be detected by thinlayer chromatography. Using this assay, we investigated techniques designed to remove carrier ampholytes from an electrofocused protein. Removal of large-molecular-weight components from carrier ampholytes by dialysis through a 3500 M_r cutoff membrane did not facilitate separation of carrier ampholytes from streptococcal pyrogenic exotoxin type C by dialysis or gel chromatography. Also, this protein binds irreversibly to mixed-bed ion-exchange resin. The best method for separating carrier ampholytes from streptococcal pyrogenic exotoxin type C was by electrodialysis at pH 4.0. Following electrodialysis, estimated carrier ampholyte contamination in this protein was less than 1 part in 500 parts (by weight).     

Human colorectal tumours in short-term organ culture A stathmokinetic study

Abstract. Short-term organ culture, using a technique to preserve epithelial/stromal interaction and metabolism, is a useful technique for carrying out kinetic studies on human colorectal carcinoma and adjacent normal mucosa, providing initial perturbations of proliferative indices are allowed to settle. Tumours require 3.0 μg/ml vincristine for complete metaphase arrest compared with mucosa, which needs 0.5 μg/ml, a 6-fold difference. Using a stathmokinetic technique, the birth rate of tumour cells is 10.21 cells/1000 cells per hr, compared with 7.73 cells/1000 cells per hr for mucosa, a statistically significant difference ( P < 0.01).     

Function of an internal bacteriophage T7 core during assembly of a T7 procapsid.

A DNA-free, proteinaceous procapsid of bacteriophage T7 (capsid I) has been shown in previous studies to consist of an external, spherical shell (envelope) and an internal, cylindrical core with fibrous projections that connect the core to the envelope. To determine the role of the core in assembly of the envelope of capsid I, the kinetics of appearance of capsid I and possible intermediates in capsid I assembly (AG particles) were determined in the presence and absence of the core. For obtaining these data, agarose gel electrophoresis was used and appeared to be a technique more accurate and efficient than techniques used for obtaining similar data in the past. The results of these experiments were: (i) in the presence of the core, AG particles behaved kinetically as intermediates in the assembly of capsid I; (ii) in the absence of the core, assembly of capsid I terminated prematurely and AG particles accumulated. These and other data have been interpreted by assuming that: AG particles are breakdown products of precursors of capsid I; these precursors have uncorrected errors in the assembly of their envelope; and a function of the core is to correct these errors.     

Isolation of an Hfr donor of Pseudomonas aeruginosa PAO by insertion of the plasmid RP1 into the tryptophan synthase gene

Summary A derivative of the IncP-1 plasmid RP1, temperature-sensitive for maintenance, was inserted into the Pseudomonas aeruginosa chromosome by selection for a plasmid marker (carbenicillin resistance) at nonppermissive temperature. In one strain, PAO 1000, the plasmid was stably integrated in the trpA, B gene cluster mapped at 27 min, as shown by the following evidence. (i) Trp⁺ transductants lost all plasmid markers. (ii) Cleared lysates of PAO 1000 showed no plasmid band typical of the autonomous RP1 in agarose gel electrophoresis. (iii) No transfer of carbenicillin resistance by PAO 1000 was detectable. (iv) PAO 1000 mobilised the chromosome from an origin at, or very near, the plasmid insertion site with high frequency (recovery of proximal markers 10^–3 per donor). Matings on the plate with and without interruption of conjugation showed that chromosome transfer was unidirectional. (v) Recombinants from PAO 1000-mediated crosses did not inherit plasmid markers or the trpA, B mutation. A derivative of PAO 1000 was obtained which had lost the Hfr property and all plasmid markers except carbenicillin resistance. This strain (PAO 1001), when carrying the autonomous RP1 plasmid, was capable of unidirectional chromosome mobilisation like PAO 1000, but with 50-fold lower efficiency. We propose that integration of the temperature-sensitive RP1 plasmid in PAO 1000 occurred via transposition of Tnl, the element specifying carbenicillin resistance.     

Systematic variation in amino acid compositions of grass caryopses

Variation in amino acid patterns of 121 species (72 genera) of grass caryopses is extensively consistent with taxonomic groupings. The patterns of pooids and chloridoids are distinguishable from one another and from those of eu-panicoids and andropogonoids; the bamboos, Oryza, Stipeae, Ehrharta and Microlaena, which share certain morphological and anatomical features, also share a characteristic amino acid profile, while profiles of danthonoioids, Triodia and Aristida are clearly non-pooid. Caryopsis amino acid patterns vary independently of photosynthetic pathway. Embryos from taxonomically diverse genera all show very similar amino acid profiles, which differ strikingly from those of the endosperms, and the amino acid patterns of whole caryopses are dominated by their endosperms, which are responsible for the taxonomic variation. ‘Chemical scores’ of the caryopsis proteins, but not total protein contents, correlate to some extent with taxonomic groupings.     

Unsaturated fatty acid but not ergosterol is essential for high ethanol production in Saccharomyces

Summary The membrane lipid composition of Saccharomyces was manipulated by growing cells anaerobically with or without ergosterol and unsaturated fatty acid. Cells low in ergosterol but enriched in unsaturated fatty acid residues on membrane phospholipids produced high concentrations, 13–15.5% w/v, of ethanol at substrate conversion efficiencies of around 90%.     

A factor analysis of body build in the rat

Following a survey of the problems associated with the comparative study of measures of physique in domesticated and laboratory animals, techniques were developed for the measurement of body build in the adult albino laboratory rat (Rattus norvegicus). They involved anesthetisation of the animals and the use of calipers and a simple apparatus devised for the purpose. The 17 measures taken on 100 rats, 50 of each sex, are detailed and the reasons for excluding others given. Intercorrelations of all the measures and their reliability co-efficients, which were judged satisfactory, are presented. The tables of intercorrelations, one for each sex, were factor analysed separately, and rotations to simple structure performed. Two factors were identified, one having factor saturations on measures of body length and the other similarly defining body width. This pattern was similar for the two sexes and a single index of body build was therefore proposed in which the length of the rear foot is divided by the width of the shoulder girdle and multiplied by 100 to avoid decimals. The use of the index in other investigations is mentioned.     

Epidemiology of yellow fever virus in humans,arthropods, and non-human primates in sub-Saharan Africa: A systematic review and meta-analysis

Yellow fever (YF) has re-emerged in the last two decades causing several outbreaks in endemic countries and spreading to new receptive regions. This changing epidemiology of YF creates new challenges for global public health efforts. Yellow fever is caused by the yellow fever virus (YFV) that circulates between humans, the mosquito vector, and non-human primates (NHP). In this systematic review and meta-analysis, we review and analyse data on the case fatality rate (CFR) and prevalence of YFV in humans, and on the prevalence of YFV in arthropods, and NHP in sub-Saharan Africa (SSA). We performed a comprehensive literature search in PubMed, Web of Science, African Journal Online, and African Index Medicus databases. We included studies reporting data on the CFR and/or prevalence of YFV. Extracted data was verified and analysed using the random effect meta-analysis. We conducted subgroup, sensitivity analysis, and publication bias analyses using the random effect meta-analysis while I² statistic was employed to determine heterogeneity. This review was registered with PROSPERO under the identification CRD42021242444. The final meta-analysis included 55 studies. The overall case fatality rate due to YFV was 31.1% (18.3–45.4) in humans and pooled prevalence of YFV infection was 9.4% (6.9–12.2) in humans. Only five studies in West and East Africa detected the YFV in mosquito species of the genus Aedes and in Anopheles funestus. In NHP, YFV antibodies were found only in members of the Cercopithecidae family. Our analysis provides evidence on the ongoing circulation of the YFV in humans, Aedes mosquitoes and NHP in SSA. These observations highlight the ongoing transmission of the YFV and its potential to cause large outbreaks in SSA. As such, strategies such as those proposed by the WHO’s Eliminate Yellow Fever Epidemics (EYE) initiative are urgently needed to control and prevent yellow fever outbreaks in SSA.