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.     

The surgical treatment of necrobiosis lipoidica diabeticorum.

We review the literature on the surgical treatment of necrobiosis lipoidica diabeticorum, and we describe 7 cases treated at Stanford University Medical Center. Experiences with them prompt us to recommend surgical excision of the lesions down to the deep fascia, ligation of the associated perforating blood vessels, and the use of split-skin grafts to cover the defects. There were no recurrences when we did all these things.     

Identification of a second trans-acting gene controlling maltose fermentation in Saccharomyces carlsbergensis.

Maltose fermentation in Saccharomyces spp. requires the presence of a dominant MAL locus. The MAL6 locus has been cloned and shown to encode the structural genes for maltose permease (MAL61), maltase (MAL62), and a positively acting regulatory gene (MAL63). Induction of the MAL61 and MAL62 gene products requires the presence of maltose and the MAL63 gene. Mutations within the MAL63 gene produce nonfermenting strains unable to induce the two structural gene products. Reversion of these mal63 nonfermenters to maltose fermenters nearly always leads to the constitutive expression of maltase and maltose permease, and constitutivity is always linked to MAL6. We demonstrated that for one such revertant, strain C2, constitutivity did not require the MAL63 gene, since deletion disruption of this gene did not affect the constitutive expression of the structural genes. In addition, constitutivity was trans acting. Deletion disruption of the MAL6-linked structural genes for maltase and maltose permease in this strain did not affect the constitutive expression of a second, unlinked maltase structural gene. We isolated new maltose-fermenting revertants of a nonfermenting strain which carried a deletion disruption of the MAL63 gene. All 16 revertants isolated expressed maltase constitutively. In one revertant studied in detail, strain R10, constitutive expression was demonstrated to be linked to MAL6, semidominant, trans acting, and residing outside the MAL63-MAL61-MAL62 genes. From these studies we propose the existence of a second trans-acting regulatory gene at the MAL6 locus. We call this new gene MAL64. We mapped the MAL64 gene 2.3 centimorgans to the left of MAL63. The role of the MAL64 gene product in maltose fermentation is discussed.     

Aminoacyl-tRNA synthetases: inter-site interaction as a possible proofreading mechanism

Smooth muscle cell energetics of taenia caeci during relaxation, activity and maximal contraction were investigated using ³¹P-NMR. In relaxed muscle obtained in calcium-free medium, [ATP], [phosphocreatine] and [sugar phosphate] were 4.4 mM, 7.7 mM and 2.8 mM, respectively. There was only a small difference in the energetics of spontaneously active and maximally contracted muscles, but under both conditions substantial changes occurred as compared with relaxed muscles. The internal pH in relaxed muscle was found to be 7.05, which acidified to 6.5 during contraction. The level of sugar phosphates was found to be not a limiting factor in energetics.