Thermal acclimation in the fresh water planarians,Dugesia tigrina and D. dorotocephala

The fecundity of two British populations of the freshwater crayfish Austropotamobius pallipes was examined. A number of maternal-size-related variables were correlated with counts of pleopodal eggs per female. Egg numbers did not decrease with increasing time from initial laying. Ovarian egg counts were considerably higher than expected pleopodal egg numbers. The influence of locational parameters is discussed and regional comparisons made.     

Biofeedback treatment of dysmenorrhea

Nine dysmenorrheic women were run in EMG and thermal biofeedback procedures with concurrent autogenic relaxation practice. Significant reductions in subjective estimates of symptomology associated with dysmenorrhea were noted in all subjects. EMG levels correlated positively with the reductions in symptoms. Thermal levels did not correlate with EMG. In fact no consistent patterns in thermal measures were noted. However, thermal biofeedback cannot be ruled out as an effective treatment for dysmenorrhea since reductions in symptoms occurred during thermal biofeedback training. Another significant aspect of the present study is the effectiveness of long treatment procedures. A six month period was employed and significant reductions in symptoms were noted following two months of biofeedback treatment. Finally, the importance of beginning biofeedback treatment prior to onset of menstrual symptoms is indicated.     

Characterization of DNA methylation in the rat

In the rat, differentiation and cell proliferation both affect DNA methylation. We studied 5-methylcytosine at the inner cytosine of the sequence C-C-G-G, a common methylation site, using endonuclease MspI (which cleaves C-C-G-G- and C-^mC-G-G), and its isoschizomer HpaII (which cleaves only C-C-G-G). DNA from all tissues and cell lines studied was methylated at C-C-G-G, at levels ranging from 45 to 80%, but the methylation sites were not distributed uniformly. Our analysis suggests a model in which cells contain variable amounts of three DNA methylation states, averaging 30–40, 70–80 and 95–100% methylation, respectively. One biological parameter that alters methylation is the prolferative state of the cell. We observed that NRK, a non-transformed cell line, increased its DNA methylation from 45 to 67% when monolayer cultures became confluent and non-dividing. We also observed that a class of repetitive DNA was completely methylated in DNA from all sources except a transformed cell line.     

The influence of exogenously supplied sucrose on glutamine synthetase and glutamate dehydrogenase levels in excisedPisum sativum roots

Glutamine synthetase (GS) level is positively influenced by exogenously supplied sucrose in isolated pea roots (similarly as nitrate reductase - NR), glutamate dehydrogenase (GDH) level negatively. Comparison with previous results shows that GS level decreases more slowly than NR level when sucrose is omitted from the medium; the rate of changes in GS level corresponds rather to that in GDH level. The increase in GDH level in the tips of isolated roots cultivated in the medium lacking sucrose stops after approx. 24 h, but continues for at least 72 h in more mature root parts. GS level decreases during the first 24 h in the tips of isolated roots (compared with roots of intact seedlings) cultivated both with sucrose and without it (without sucrose more), however it again rises in the course of further cultivation with sucrose. The differences in GS and GDH levels caused by omission of sucrose are small in isolated roots from which root tips were removed, the difference in NR level in decapitated roots is similar to that found in isolated roots with root tips left. Decapitated isolated roots cultivated without sucrose contain higher amounts of soluble sugars than corresponding roots with root tips left. These facts are dismissed with regard to sugar consumption, transport, and compartmentalisation, and with respect to production in root tips and other plant parts of unknown compounds involved in GS and GDH regulation. The results obtained suggest that GDH functions in pea roots in the deaminating direction.     

Membrane-integration Characteristics of Two ABC Transporters, CFTR and P-glycoprotein

To what extent do corresponding transmembrane helices in related integral membrane proteins have different membrane-insertion characteristics? Here, we compare, side-by-side, the membrane insertion characteristics of the 12 transmembrane helices in the adenosine triphosphate-binding cassette (ABC) transporters, P-glycoprotein (P-gp) and the cystic fibrosis transmembrane conductance regulator (CFTR). Our results show that 10 of the 12 CFTR transmembrane segments can insert independently into the ER membrane. In contrast, only three of the P-gp transmembrane segments are independently stable in the membrane, while the majority depend on the presence of neighboring loops and/or transmembrane segments for efficient insertion. Membrane-insertion characteristics can thus vary widely between related proteins.     

A cluster of fourteen genes from enteropathogenic Escherichia coli is sufficient for the biogenesis of a type IV pilus

Enteropathogenic Escherichia coli (EPEC) adhere to epithelial cells in microcolonies, a pattern termed localized adherence (LA). LA is dependent upon the presence of 50–70MDa plasmids, termed EPEC adherence factor (EAF) plasmids. Expression of an EAF plasm id-encoded type IV fimbria, the bundle-forming pilus (BFP), is associated with the LA phenotype. TnphoA insertions in bfpA, the gene encoding the major structural subunit of the BFP, abolish LA. While bfpA::TnphoA mutants cannot be complemented for LA by plasmids carrying the bfpA gene alone in trans, this work shows that they can be complemented by plasmids carrying the bfpA gene, as well as approximately 10kb of downstream sequence, suggesting that such mutations have polar effects on downstream genes. The identification and characterization of a cluster of 13 genes immediately downstream of bfpA are described. The introduction into a laboratory Escherichia coli strain of a plasmid containing these 14 bfp gene cluster genes, along with pJPN14, a plasmid containing another fragment derived from the EAF plasmid, confers LA ability and BFP biogenesis. However, when a mutation is introduced into the last gene of the bfp cluster, neither LA nor BFP biogenesis is conferred. This work also provides evidence to show that the fragment cloned in pJPN14 encodes a factor(s) which results in increased levels of the pilin protein. Finally, it is shown that expression of the 14 genes in the bfp cluster from an IPTG-inducible promoter, in the absence of pJPN14, is sufficient to reconstitute BFP biogenesis in a laboratory E. cob strain, but is insufficient for LA. This is the first report demonstrating the reconstitution of a type IV pilus in a laboratory E. coli strain with a defined set of genes. The 8FP system should prove to be a useful model for studying the molecular mechanisms of type IV pilus biogenesis.     

A dynamic and intricate regulatory network determines Pseudomonas aeruginosa virulence

Pseudomonas aeruginosa is a metabolically versatile bacterium that is found in a wide range of biotic and abiotic habitats. It is a major human opportunistic pathogen causing numerous acute and chronic infections. The critical traits contributing to the pathogenic potential of P. aeruginosa are the production of a myriad of virulence factors, formation of biofilms and antibiotic resistance. Expression of these traits is under stringent regulation, and it responds to largely unidentified environmental signals. This review is focused on providing a global picture of virulence gene regulation in P. aeruginosa. In addition to key regulatory pathways that control the transition from acute to chronic infection phenotypes, some regulators have been identified that modulate multiple virulence mechanisms. Despite of a propensity for chaotic behaviour, no chaotic motifs were readily observed in the P. aeruginosa virulence regulatory network. Having a ‘birds-eye’ view of the regulatory cascades provides the forum opportunities to pose questions, formulate hypotheses and evaluate theories in elucidating P. aeruginosa pathogenesis. Understanding the mechanisms involved in making P. aeruginosa a successful pathogen is essential in helping devise control strategies.     

Inhibition of acid production in Streptococcus mutans R9: Inhibition constants and reversibility

Abstract The pac gene encoding the penicillin G acylase (PGA) of Bacillus megaterium ATCC 14945 has been cloned in Escherichia coli HB101 ( proA, leuB ) using a selective minimal medium containing phenylacetyl-L-leucine instead of L-leucine. The nucleotide sequence of this gene has been determined and contains an open reading frame of 2406 nucleotides. The deduced amino acid sequence shows significant similarity with other β-lactam acylases. Although the PGA of B. megaterium is extracellular, the enzyme produced in E. coli appears to have a cytoplasmic localization.     

Vertebral Bomb Radiocarbon Suggests Extreme Longevity in White Sharks

Conservation and management efforts for white sharks (Carcharodon carcharias) remain hampered by a lack of basic demographic information including age and growth rates. Sharks are typically aged by counting growth bands sequentially deposited in their vertebrae, but the assumption of annual deposition of these band pairs requires testing. We compared radiocarbon (Δ¹⁴C) values in vertebrae from four female and four male white sharks from the northwestern Atlantic Ocean (NWA) with reference chronologies documenting the marine uptake of ¹⁴C produced by atmospheric testing of thermonuclear devices to generate the first radiocarbon age estimates for adult white sharks. Age estimates were up to 40 years old for the largest female (fork length [FL]: 526 cm) and 73 years old for the largest male (FL: 493 cm). Our results dramatically extend the maximum age and longevity of white sharks compared to earlier studies, hint at possible sexual dimorphism in growth rates, and raise concerns that white shark populations are considerably more sensitive to human-induced mortality than previously thought.