A comparison between formol saline and Mirsky's fluid as fixatives for nematodes

In order to evaluate the fixing properties of Mirsky's fluid on nematodes, a comparison was made with formaldehyde. On two occasions, nematodes recovered from the abomasa of calves were fixed in each of three of the following fluids: 5% formol saline, 10% formol saline, 5% Mirsky's fluid and 10% Mirsky's fluid. Based on measurements of length and microscopical examination of over 800 nematodes on each occasion, the authors concluded that Mirsky's fluid conferred no advantages over 5% formol saline or 10% formol saline for fixing nematodes.     

Prolidase deficiency: biochemical classification of alleles

Prolidase (E.C.3.4.13.9) is a homodimeric enzyme encoded at a locus on chromosome 19. Prolidase deficiency is an autosomal recessive disorder with a highly variable clinical phenotype. We purified prolidase to homogeneity from normal human fibroblasts, raised a monospecific rabbit antiserum, and studied biosynthesis of the subunit in normal and prolidase--deficient fibroblasts. Pulse-chase immunoprecipitation experiments showed that the subunit is synthesized and retained in cytosol as a 58-KDa polypeptide. Three types of mutations were identified in six prolidase-deficient cell strains; half conferred a CRM-negative phenotype, while the CRM-positive mutations were of two types, one mutation encoding an enlarged subunit (60 KDa) and the others associated with subunits of normal size. Complementation analysis indicated that these mutations map to one locus. Normal subjects and obligate heterozygotes expressing CRM-negative mutations had thermostable prolidase activity at 50 degrees C in cell extracts, whereas heterozygotes expressing CRM-positive mutations had thermolabile activity under the same condition, implying negative allelic complementation in the putative heterodimer. The occurrence of prolidase-like activity about 5% of normal in amount but with a preference for substrate different from normal, in cells homozygous (or compound) for CRM-negative mutations, identified an alternative cleavage activity not encoded at the prolidase locus. Allelic heterogeneity at the major locus and the amount of alternative peptidase activity encoded elsewhere appear to be determinants of the associated and heterogeneous clinical phenotype.     

Sodium,protons, and energy coupling in the methanogenic bacteria

In this review, I focus on the bioenergetics of the methanogenic bacteria, with particular attention directed to the roles of transmembrane electrochemical gradients of sodium and proton. In addition, the mechanism of coupling ATP synthesis to methanogenic electron transfer is addressed. Evidence is reviewed which suggests that the methanogens possess great diversity in their bioenergetic machinery. In particular, in some methanogens the primary ion which is translocated coupled to metabolic energy is the proton, while others appear to utilize sodium. In addition, ATP synthesis driven by methanogenic electron transfer is accomplished in some organisms by a chemiosmotic mechanism and is coupled by a more direct mechanism in others. A possible explanation for this diversity (which is consistent with the relatedness of these organisms to each other and to other members of the Archaebacteria as determined by molecular biological techniques) is discussed.     

Rhesus Monkeys (Macaca mulatta) Do Recognize Themselves in the Mirror: Implications for the Evolution of Self-Recognition

Self-recognition in front of a mirror is used as an indicator of self-awareness. Along with humans, some chimpanzees and orangutans have been shown to be self-aware using the mark test. Monkeys are conspicuously absent from this list because they fail the mark test and show persistent signs of social responses to mirrors despite prolonged exposure, which has been interpreted as evidence of a cognitive divide between hominoids and other species. In stark contrast with those reports, the rhesus monkeys in this study, who had been prepared for electrophysiological recordings with a head implant, showed consistent self-directed behaviors in front of the mirror and showed social responses that subsided quickly during the first experimental session. The self-directed behaviors, which were performed in front of the mirror and did not take place in its absence, included extensive observation of the implant and genital areas that cannot be observed directly without a mirror. We hypothesize that the head implant, a most salient mark, prompted the monkeys to overcome gaze aversion inhibition or lack of interest in order to look and examine themselves in front of the mirror. The results of this study demonstrate that rhesus monkeys do recognize themselves in the mirror and, therefore, have some form of self-awareness. Accordingly, instead of a cognitive divide, they support the notion of an evolutionary continuity of mental functions.     

Target highlights in CASP13: Experimental target structures through the eyes of their authors

The functional and biological significance of selected CASP13 targets are described by the authors of the structures. The structural biologists discuss the most interesting structural features of the target proteins and assess whether these features were correctly reproduced in the predictions submitted to the CASP13 experiment.     

Changes in the content and distribution, in different organs, of the flavour precursors, the S-alk(en)yl-L-cysteine sulphoxides, during seedling development of onions (Allium cepa) grown under light and dark regimes

Flavour precursors accumulated rapidly in onion seedlings ( Allium cepa L. cv. Pukekohe Longkeeper, May and Ryan) after emergence of the cotyledon. (±)-S-1-Propyl-L-cysteine sulphoxide, found mainly in the shoots, was the predominant flavour precursor. (±) Trans -S-1-propenyl-L-cysteine sulphoxide was important during very early seedling growth when very high concentrations were reported in the root and hypocotyl. (±)-S-1-Methyl-L-cysteine sulphoxide, a minor component in seedlings grown under a normal light regime, was significant during early cotyledon development in seedlings grown in the dark. It is concluded that onion seedlings would be a suitable tissue in which to investigate the biosynthetic pathways of the S-alk(en)yl-L-cysteine sulphoxides.     

Millipore Filtration of Conjugating Bacterial Cells, with Epoxy Embedding for Electron Microscopy

Broth cultures of Escherichia coli, strains Hfr G6 and F^- 464 grown separately, were mixed (2 ml of each) and the mixture filtered through a 0.45 μ pore size, 25 mm diameter, MF-Millipore membrane. The membrane was placed, cell side up, on a nutrient agar plate and incubated 15 min at 37 C. Processing in the customary manner to include fixation, staining and epoxy embedding for electron microscopy followed. The technique provides greater concentration of cells, allows less opportunity for separation of conjugating cells and is less time consuming than procedures involving concentration by centrifugation and enclosure in agar as prerequisities to resin embedding.