Formaldehyde fixation of cells does not greatly reduce the ability to amplify cellular DNA

Formaldehyde fixation of cells is routinely used to study DNA-protein interactions in vivo. In these studies, DNA is often analyzed using a polymerase chain reaction technique. Although it is known that formaldehyde can damage DNA, no studies have been performed so far to compare the efficiency of DNA amplification between normal and fixed cells. Here we show that formaldehyde fixation results in a 15% to 20% reduction in the ability to amplify cellular DNA. The loss of amplifiability is independent of the length of the amplification region and the degree to which DNA is compacted on packaging into chromatin.     

Using Principal Components and Factor Analysis in Animal Behaviour Research: Caveats and Guidelines

Principal component (PCA) and factor analysis (FA) are widely used in animal behaviour research. However, many authors automatically follow questionable practices implemented by default in general‐purpose statistical software. Worse still, the results of such analyses in research reports typically omit many crucial details which may hamper their evaluation. This article provides simple non‐technical guidelines for PCA and FA. A standard for reporting the results of these analyses is suggested. Studies using PCA and FA must report: (1) whether the correlation or covariance matrix was used; (2) sample size, preferably as a footnote to the table of factor loadings; (3) indices of sampling adequacy; (4) how the number of factors was assessed; (5) communalities when sample size is small; (6) details of factor rotation; (7) if factor scores are computed, present determinacy indices; (8) preferably they should publish the original correlation matrix.     

The Influence of Texting Language on Grammar and Executive Functions in Primary School Children

When sending text messages on their mobile phone to friends, children often use a special type of register, which is called textese. This register allows the omission of words and the use of textisms: instances of non-standard written language such as 4ever (forever). Previous studies have shown that textese has a positive effect on children’s literacy abilities. In addition, it is possible that children’s grammar system is affected by textese as well, as grammar rules are often transgressed in this register. Therefore, the main aim of this study was to investigate whether the use of textese influences children’s grammar performance, and whether this effect is specific to grammar or language in general. Additionally, studies have not yet investigated the influence of textese on children’s cognitive abilities. Consequently, the secondary aim of this study was to find out whether textese affects children’s executive functions. To investigate this, 55 children between 10 and 13 years old were tested on a receptive vocabulary and grammar performance (sentence repetition) task and various tasks measuring executive functioning. In addition, text messages were elicited and the number of omissions and textisms in children’s messages were calculated. Regression analyses showed that omissions were a significant predictor of children’s grammar performance after various other variables were controlled for: the more words children omitted in their text messages, the better their performance on the grammar task. Although textisms correlated (marginally) significantly with vocabulary, grammar and selective attention scores and omissions marginally significantly with vocabulary scores, no other significant effects were obtained for measures of textese in the regression analyses: neither for the language outcomes, nor for the executive function tasks. Hence, our results show that textese is positively related to children’s grammar performance. On the other hand, use of textese does not affect—positively nor negatively—children’s executive functions.     

Pr-SNTX,a short-chain three-finger toxin from Papuan pigmy mulga snake,is an antagonist of muscle-type nicotinic acetylcholine receptor (α2βδε)

Three-finger toxins (3FTxs) are one of the major components in snake venoms. In this study, we isolated a cDNA encoding a short-chain 3FTx, Pr-SNTX, from Pseudechis rossignolii. The amino acid sequence of Pr-SNTX is nearly identical to that of its ortholog in Pseudechis australis. Pr-SNTX protein inhibited muscle-type (α₂βδε), but not neuronal α7 nicotinic acetylcholine receptor (nAChR) activity.     

Rearrangement of nucleoli in hepatocytes stimulated for proliferation and enhancement of their transcription function

The nucleoli of normally functioning guinea-pig hepatocytes that have a nucleolonemal (strand-like) organization differ from identical nucleoli of other cells. Their nucleolonema consists as a rule of a fibrillar component with 45S RNA and is poor in granulas that contain pre-rNA molecules of an intermediate size and 28S rRNA, a dense fibrillar component with nascent rRNPs in its composition was not revealed. In hepatocytes stimulated by a 2/3 liver resection rearrangements in nucleoli were found. This brought to a conclusion that rRNA metabolism undergoes some changes. In 2.5 and 5 hours after the resection the hepatocytes' nucleoli were characteristic of a greater thickness of strands and a smaller size of vacuoles, appearance of distinct zones of the dense fibrillar component and an increased amount of RNP-granules. All these observations taken together point out at an increased synthesis and processing of rRNA at early stages of the prereplicative period. In 9 hours the character of changes in nucleoli was different: the vacuoles were considerably widened, whereas the thickness of strands that consisted of a well-expressed dense fibrillar, fibrillar and granular components was lesser. Such rearrangement points out at an increased transport of preribosomes from the nucleolus, a high level of synthesis and processing of nascent RNP-product being maintained. The changes of nucleolar RNP-component were followed by appearance of greater blocks of perinucleolar condensed chromatin, which may be connected with "cutting-off" some tissue-specific genes and initiation of functioning of the mitotic operon genes.     

Genetic transformation of mouse cultured cells with the help of high-velocity mechanical DNA injection

NIH 3T3 mouse cells were transfected by the plasmid pSV3neo (G418-resistant) with the help of high-velocity mechanical DNA injection based on the principle of bombarding cells with tungsten particles covered with the DNA. Stable transformants were obtained. Dot-hybridization and Southern analysis revealed the integration into the genome of 5-20 copies per cell of original plasmid DNA. The plasmid DNA was shown to have tandem organization.     

DNA synthesis in heterokaryons obtained by the fusion of polymorphonuclear leukocytes and cultured cells possessing different proliferative potentials

Heterokaryons between terminally differentiated polymorphonuclear leukocytes (PL) and culture cells of different proliferative potentials: mouse and rat embryo fibroblasts (EFM, EFR); immortal cells NIH 3T3 and E2; malignant cells NCC2, L929, He239 and SV 3T3,--were obtained by means of electrofusion. Radioautographic study of 3H-thymidine incorporation in the nuclei of heterokaryons showed that all the cells taken for fusion were able to induce reactivation of DNA synthesis in PL nuclei, however, with different rates: 7-37% for EFM and NIH 3T3 and 20-40% for malignant cells. The presence of oncogenes Elan in E2 cells and ras in NCC2 cells increased the rate of PL reactivation approximately twice as compared with the cells of original lines (EFR and NIH 3T3, correspondingly). In parallel to reactivation of DNA synthesis in PL nuclei inhibition of the synthesis in culture cell nuclei in the same heterokaryons was found. The rate of inhibition was about 70% for non-malignant and 23, 40 and 18% for NCC2, L and SV 3T3 cells, respectively. He239 cells, transformed by a temperature-dependent mutant of virus SV40 showed at permissive temperature the increased capacity of inducing reactivation of PL nuclei, though He239 cells susceptibility to inhibitory action of PL nuclei did not change with temperature. According to the behaviour in heterokaryons PL were found to be similar to chick erythrocytes, but differing from them by a pronounced inhibiting effect upon DNA synthesis in the nuclei of malignant cells.     

Cytogenetic analysis of forms produced by crossing hexaploid triticale with common wheat

Summary Hexaploid triticales were crossed with common wheats, and the resultant froms were selected for either triticale (AD 213/5-80) or common wheat (lines 381/80, 391/80, 393/80). The cytogenetic analysis showed that all forms differ in their chromosome composition. Triticale AD 213/5-80 and wheat line 381/80 were stable forms with 2n = 6x = 42. Lines 391/80 and 393/80 were cytologically unstable. In triticale AD 213/5-80, a 2R (2D) chromosome substitution was found. Each of the three wheat lines had a chromosome formed by the translocation of the short arm of IR into the long arm of the IB chromosome. In line 381/80, this chromosome seems to be inherited from the Kavkaz wheat variety. In lines 391/80 and 393/80, this chromosome apparently formed de novo since the parent forms did not have it. The karyotype of line 381/80 was found to contain rye chromosomes 4R/7R, 5R and 7R/4R. About 15% of the cells in line 391/80 contained an isochromosome for the 5R short arm and also a chromosome which arose from the translocation of the long arms of the 5D and 5R chromosomes. About one-third of the cells in the common wheat line 393/80 contained the 5R chromosome. This chromosome was normal or rearranged. Practical applications of the C-banding technique in the breeding of triticale is discussed.