The genetic background of gallstone formation: An update

Gallstone disease is one of the most prevalent gastrointestinal diseases with a substantial burden to health care systems that is expected to increase in ageing populations at risk. This review summarizes recent data on the genetic background of cholesterol gallstones and the role of biliary lipid composition. Three previously unknown non-synonymous mutations in the ABCB4 gene encoding the hepatobiliary phospholipid-flippase MDR3 are presented.     

Assessment of heterologous butyrate and butanol pathway activity by measurement of intracellular pathway intermediates in recombinant Escherichia coli

In clostridia, n-butanol production from carbohydrates at yields of up to 76% of the theoretical maximum and at titers of up to 13 g/L has been reported. However, in Escherichia coli, several groups have reported butyric acid or butanol production from recombinant expression of clostridial genes, at much lower titers and yields. To pinpoint deficient steps in the recombinant pathway, we developed an analytical procedure for the determination of intracellular pools of key pathway intermediates and applied the technique to the analysis of three sets of E. coli strains expressing various combinations of butyrate biosynthesis genes. Low expression levels of the hbd-encoded S-3-hydroxybutyryl-CoA dehydrogenase were insufficient to convert acetyl-CoA to 3-hydroxybutyryl-CoA, indicating that hbd was a rate-limiting step in the production of butyryl-CoA. Increasing hbd expression alleviated this bottleneck, but in resulting strains, our pool size measurements and thermodynamic analysis showed that the reaction step catalyzed by the bcd-encoded butyryl-CoA dehydrogenase was rate-limiting. E. coli strains expressing both hbd and ptb-buk produced crotonic acid as a byproduct, but this byproduct was not observed with expression of related genes from non-clostridial organisms. Our thermodynamic interpretation of pool size measurements is applicable to the analysis of other metabolic pathways.     

Microsomal epoxide hydrolase expression in the endometrial uterine corpus is regulated by progesterone during the menstrual cycle

We have shown previously that high expression levels of microsomal epoxide hydrolase (mEH) correlate with a poor prognosis of breast cancer patients receiving tamoxifen, suggesting that enhanced mEH expression could lead to antiestrogen resistance (Fritz et al. in J Clin Oncol 19:3–9, 2001). Thus, the purpose of this study was to gain insights into the role of mEH in hormone-responsive tissues. We analyzed biopsy samples of the endometrium by immunohistochemical staining, pointing to a regulation of mEH during the menstrual cycle: during the first half mEH expression was low, increased during the second half and reached highest levels during pregnancy. Additionally, the progesterone receptor (PR) positive human endometrial cell lines IKPRAB-36 (estrogene receptor α [ERα] negative) and ECC1-PRAB72 (ERα positive) were chosen to further investigate the hormonal regulation of mEH expression. Western Blot and quantitative RT-PCR analysis revealed an increase of mEH expression after treatment with medroxy-progesterone 17-acetate (MPA) in the ERα containing ECC1-PRAB72 cells. In contrast our results suggest that MPA had no influence on the mEH protein level in the ERα- IKPRAB-36 cells. In conclusion, mEH expression is regulated by progesterone in the presence of both PRs and ERα.     

Echocardiographic assessment of subclinical left ventricular eccentric hypertrophy in adult-onset GHD patients by geometric remodeling: an observational case-control study

Background

Most patients with growth hormone deficiency (GHD) show high body mass index. Overweight subjects, but GHD patients, were demonstrated to have high left ventricular mass index (LVMi) and abnormal LV geometric remodeling. We sought to study these characteristics in a group of GHD patients, in an attempt to establish the BMI-independent role of GHD.

Methods

Fifty-four patients, 28 F and 26 M, aged 45.9 ± 13.1, with adult-onset GHD (pituitary adenomas 48.2%, empty sella 27.8%, pituitary inflammation 5.5%, cranio-pharyngioma 3.7%, not identified pathogenesis 14.8%) were enrolled. To minimize any possible interferences of BMI on the aim of this study, the control group included 20 age- and weight-matched healthy subjects. The LV geometry was identified by the relationship between LVMi (cut-off 125 g/m²) and relative wall thickness (cut-off 0.45) at echocardiography.

Results

There was no significant between-group difference in resting cardiac morphology and function, nor when considering age-related discrepancy. The majority of patients had normal-low LVM/LVMi, but about one fourth of them showed higher values. These findings correlated to relatively high circulating IGF-1 and systolic blood pressure at rest. The main LV geometric pattern was eccentric hypertrophy in 22% of GHD population (26% of with severe GHD) and in 15% of controls (p = NS).

Conclusion

Though the lack of significant differences in resting LV morphology and function, about 25% of GHD patients showed high LVMi (consisting of eccentric hypertrophy), not dissimilarly to overweight controls. This finding, which prognostic role is well known in obese and hypertensive patients, is worthy to be investigated in GHD patients through wider controlled trials.     

Analysis of polyhydroxybutyrate flux limitations by systematic genetic and metabolic perturbations

Poly-3-hydroxybutyrate (PHB) titers in Escherichia coli have benefited from 10+ years of metabolic engineering. In the majority of studies, PHB content, expressed as percent PHB (dry cell weight), is increased, although this increase can be explained by decreases in growth rate or increases in PHB flux. In this study, growth rate and PHB flux were quantified directly in response to systematic manipulation of (1) gene expression in the product-forming pathway and (2) growth rates in a nitrogen-limited chemostat. Gene expression manipulation revealed acetoacetyl-CoA reductase (phaB) limits flux to PHB, although overexpression of the entire pathway pushed the flux even higher. These increases in PHB flux are accompanied by decreases in growth rate, which can be explained by carbon diversion, rather than toxic effects of the PHB pathway. In chemostats, PHB flux was insensitive to growth rate. These results imply that PHB flux is primarily controlled by the expression levels of the product forming pathway and not by the availability of precursors. These results confirm prior in vitro measurements and metabolic models and show expression level is a major affecter of PHB flux.     

Frequency and fidelity of alien chromosome transmission in Gossypium hexaploid bridging populations.

The Australian diploid Gossypium species possess traits of potential agronomical value, such as gossypol-free seeds and Fusarium wilt resistance. However, they belong to the tertiary germplasm pool, which is the most difficult group of species from which to introgress genes into G. barbadense L. and G. hirsutum L. Interspecific triploid hybrids can be generated but they are sterile. The sterility barrier can be overcome using synthetic polyploids as introgression bridges, but whether there is sufficient homoeologous chromosome interaction at meiosis to allow recombination is still an open question. To ascertain, genetically, observable levels of homoeologous introgression, 2 synthetic hexaploid lines (2x G. hirsutum x G. australe and 2x G. hirsutum x G. sturtianum) were crossed to G. hirsutum to generate pentaploid F1 plants that, in turn, were backcrossed to G. hirsutum to generate BC1 and BC2 multiple alien chromosome addition lines (MACALs). Gossypium australe F. Muell. and G. sturtianum Willis chromosome-specific markers were used to track the frequency and fidelity of chromosome transmission to the BC1 and BC2 MACALs. The chromosomal location of the AFLP markers was determined by their distribution among the MACALs and confirmed in parental F2 families. Roughly half the available chromosomes were transmitted to the G. hirsutum x G. australe (54%) and G. hirsutum x G. sturtianum (52%) BC1 MACALs. The BC2 MACAL families again inherited about half of the available chromosomes. There were, however, notable exceptions for specific chromosomes. Some chromosomes were preferentially eliminated, while others were preferentially transmitted. Consistent with the genomic stability of Gossypium synthetic polyploids, the de novo loss or gain of AFLP fragments was rarely observed. While restructuring of the donor G. australe and G. sturtianum chromosomes was observed, this is more likely the result of chromatin loss, and no clear cases of introgression of donor chromatin into the recipient G. hirsutum genome were observed.     

The coexistence of Escherichia coli serotype O157:H7 and its specific bacteriophage in continuous culture

For the development of phage therapy, systematic understanding mechanisms of bacteriophage resistance will be required. We describe a new strain of Escherichia coli O157:H7, named Mu(L), which stably co-exists with the O157:H7-specific lytic bacteriophage PP01. Chemostat cultures of E. coli O157:H7 infected with PP01 showed unchanging cell concentration, but phage concentrations which increased by approximately 10(8) PFU mL(-1). However, the latent period, burst size, and growth rate of Mu(L) were the same as in a PP01-susceptible strain. The binding rate of PP01 to the cell surface was diminished 8.5-fold in Mu(L). By observation of the binding of fluorescently labeled O157:H7-specific phage to individual Mu(L) cells, we found that clonal Mu(L) cultures were heterogeneous in their ability to bind bacteriophage. 15% of the Mu(L) population was completely resistant to PP01 infection. Mu(L) also co-existed with bacteriophages unrelated to PP01. Broad-range phage resistance by clonal heterogeneity represents a new class of bacteria-phage interactions.