Heat resistance of Klebsiella pneumoniae in media with various sucrose concentrations

Summary The heat resistance of Klebsiella pneumoniae, an organism of widespread occurrence in nature has been determined in media containing various amounts of sucrose at temperatures between 47° and 59°C.In the presence of sucrose and at all temperatures the inactivation curves show a fast initial drop (logarithmic phase) in the number of survivors followed by a less rapid one (tail phase). The influence of the sucrose concentration can be described withln k _s = ln k _O – _T [sucrose] for media with more than 0.52 mol/l sucrose for the logarithmic as well as for the tail phase of inactivation.The heat-injured cells were recovered on various media to investigate the influence of the presence of small metabolites and nutrients on the shape of the inactivation curves and on the death rate. For cells heated in media without sucrose, the recovery on a rich medium was much better than on a poor one; for cells heated in media with more than 0.26 mol/l sucrose, no difference was observed between the various recovery media.The activation energies as determined on the various media are always nearly the same, which strongly suggests that the critical sites in the heat inactivation were not enzymes playing a key role in the synthesis of small molecules such as amino acids or nucleotides.     

T1 and T2 lymphocytes in primary and secondary delayed type hypersensitivity of mice. I. Contribution in the response to sheep red blood cells and to allogeneic spleen cells.

Peripheral T lymphocytes can be subdivided into two populations (T₁ and T₂ cells) based upon the short life span of T₁ cells after adult thymectomy (ATx) and sensitivity of T₂ cells to treatment with anti-thymocyte serum (ATS) in vivo. The contribution of the T₁ and T₂ cells to primary and secondary delayed type hypersensitivity (DTH) to sheep red blood cells (SRBC) and to primary DTH to allogeneic cells was studied in mice. T₂ cells were found to account for the development of the state of primary DTH responsiveness after intravenous immunization with SRBC and after subcutaneous immunization with allogeneic cells. No clear cut evidence was found that in the presence of T₂ cells DTH related T effector cells were generated from T₁ cells. In mice selectively depleted for T₁ cells by ATx, the remaining T₂ cells were capable to generate SRBC-specific T memory cells, but not in numbers as large as in non-thymectomized mice. On the other hand, T₁ cells in mice depleted for T₂ cells by ATS treatment, could give rise to normal numbers of SRBC-specific T memory cells. Apparently T₁ cells can compensate for the absence of T₂ cells during generation of T memory cells, but T₂ cells cannot do so for the loss of T₁ cells. From the time curve showing the ATx-induced decline of the population of SRBC-specific T₂ cells, involved in primary DTH responsiveness, the half life was calculated to be 6 to 7 months.     

Linking root traits and competitive success in grassland species

Background and aims

Measures of phosphorus (P) in roots recovered from soil underestimate total P accumulation below-ground by crop species since they do not account for P in unrecovered (e.g., fine) root materials. ³³P-labelling of plant root systems may allow more accurate estimation of below-ground P input by plants.

Methods

Using a stem wick-feeding technique ³³P-labelled phosphoric acid was fed in situ to canola (Brassica napus) and lupin (Lupinus angustifolius) grown in sand or loam soils in sealed pots.

Results

Recovery of ³³P was 93 % in the plant-soil system and 7 % was sorbed to the wick. Significantly more ³³P was allocated below-ground than to shoots for both species with 59–90 % of ³³P measured in recovered roots plus bulk and rhizosphere soil. ³³P in recovered roots was higher in canola than lupin regardless of soil type. The proportion of ³³P detected in soil was greater for lupin than canola grown in sand and loam (37 and 73 % lupin, 20 and 23 % canola, respectively). Estimated total below-ground P accumulation by both species was at least twice that of recovered root P and was a greater proportion of total plant P for lupin than canola.

Conclusion

Labelling roots using ³³P via stem feeding can empower quantitative estimates of total below-ground plant P and root dry matter accumulation which can improve our understanding of P distribution in soil-plant systems.

     

Jaw transformation with gain of symmetry after Dlx5/Dlx6 inactivation: Mirror of the past?

In modern vertebrates upper and lower jaws are morphologically different. Both develop from the mandibular arch, which is colonized mostly by Hox-free neural crest cells. Here we show that simultaneous inactivation of the murine homeobox genes Dlx5 and Dlx6 results in the transformation of the lower jaw into an upper jaw and in symmetry of the snout. This is the first homeotic-like transformation found in this Hox-free region after gene inactivation. A suggestive parallel comes from the paleontological record, which shows that in primitive vertebrates both jaws are essentially mirror images of each other. Our finding supports the notion that Dlx genes are homeotic genes associated with morphological novelty in the vertebrate lineage.     

Synthesis and evaluation of strand and turn modified ring-extended gramicidin S derivatives

In this paper, we describe the crystal structure of previously reported ring-extended gramicidin S (GS) derivative 2 (GS14K4), containing a d-amino acid residue in one of the β-strand regions. This structure is in agreement with a previously reported modeling study of the same molecule. The polar side chain of the additional d-amino acid residue is positioned at the same face of the molecule as the hydrophobic side chains, and we believe that because of this compound 2 is considerably less hydrophobic than extended GS derivatives in which the strand regions are exclusively composed of l-amino acids. Using this backbone structure as our benchmark we prepared a small series of ring-extended GS analogues featuring sugar amino acid dipeptide isosteres of varied hydrophobicity at the turn region. We show that via this approach hydrophobicity of extended GS analogues can be tuned without affecting the secondary structure (as observed from NMR and CD spectra). Biological evaluation reveals that hydrophobicity correlates to cell toxicity, but still bacteriolysis is induced with GS analogues that are too hydrophilic to efficiently lyse human red blood cells.     

Multilocus definition of MHC haplotypes in pedigreed cynomolgus macaques (Macaca fascicularis)

Cynomolgus macaques (Macaca fascicularis) are used widely in biomedical research, and the genetics of their MHC (Mhc-Mafa) has become the focus of considerable attention in recent years. The cohort of Indonesian pedigreed macaques that we present here was typed for Mafa-A, -B, and -DR, by sequencing, as described in earlier studies. Additionally, the DRB region of these animals was characterised by microsatellite analyses. In this study, full-length sequencing of Mafa-DPA/B and -DQA/B in these animals was performed. A total of 75 different alleles were observed; 22 of which have not previously been reported, plus 18 extended exon 2 alleles that were already known. Furthermore, two microsatellites, D6S2854 and D6S2859, were used to characterise the complex Mafa-A region. Sequencing and segregation analyses revealed that the length patterns of these microsatellites are unique for each Mafa-A haplotype. In this work, we present a pedigreed colony of approximately 120 cynomolgus macaques; all of which are typed for the most significant polymorphic MHC class I and class II markers. Offspring of these pedigreed animals are easily characterised for their MHC by microsatellite analyses on the Mafa-A and -DRB regions, which makes the cumbersome sequencing analyses redundant.     

Prostatic preneoplasia and beyond

Prostate cancer is a heterogeneous neoplasm both with regard to its development, molecular abnormalities and clinical course. For example, in the United States, 1 in 6 men is diagnosed with prostate cancer whilst only 1 in 34 dies of metastatic disease [A. Jemal, R. Siegel, E. Ward, T. Murray, J. Xu, M.J. Thun, Cancer Statistics, 2007, CA Cancer J. Clin. 57 (2007) 43-66]. In this review, we summarise novel understandings of the early molecular events in prostatic carcinogenesis that may underlie both the molecular and clinical heterogeneity. Issues covered include those related to stem cells and embryonic signalling, oncogene/tumor suppressor abnormalities, androgen signalling, apoptosis and the nature of tumor-stromal interactions. Emphasis is placed on signalling pathway abnormalities, their causation, consequences and interactions. For example, genomic abnormalities involving the TMPRSS2-ETS and PTEN loci and the resulting signalling effects suggest the importance of genomic instability as a crucial factor in the emergence of this neoplasm. Together with new insights into signalling pathways consequent to abnormalities such as these, a greater understanding of the pathophysiology involved in prostatic carcinogenesis will lead to targeted approaches for both therapy and chemoprevention in the future.