Air trapping on chest CT is associated with worse ventilation distribution in infants with cystic fibrosis diagnosed following newborn screening

Background

In school-aged children with cystic fibrosis (CF) structural lung damage assessed using chest CT is associated with abnormal ventilation distribution. The primary objective of this analysis was to determine the relationships between ventilation distribution outcomes and the presence and extent of structural damage as assessed by chest CT in infants and young children with CF.

Methods

Data of infants and young children with CF diagnosed following newborn screening consecutively reviewed between August 2005 and December 2009 were analysed. Ventilation distribution (lung clearance index and the first and second moment ratios [LCI, M₁/M₀ and M₂/M₀, respectively]), chest CT and airway pathology from bronchoalveolar lavage were determined at diagnosis and then annually. The chest CT scans were evaluated for the presence or absence of bronchiectasis and air trapping.

Results

Matched lung function, chest CT and pathology outcomes were available in 49 infants (31 male) with bronchiectasis and air trapping present in 13 (27%) and 24 (49%) infants, respectively. The presence of bronchiectasis or air trapping was associated with increased M₂/M₀ but not LCI or M₁/M₀. There was a weak, but statistically significant association between the extent of air trapping and all ventilation distribution outcomes.

Conclusion

These findings suggest that in early CF lung disease there are weak associations between ventilation distribution and lung damage from chest CT. These finding are in contrast to those reported in older children. These findings suggest that assessments of LCI could not be used to replace a chest CT scan for the assessment of structural lung disease in the first two years of life. Further research in which both MBW and chest CT outcomes are obtained is required to assess the role of ventilation distribution in tracking the progression of lung damage in infants with CF.     

FMR1 repeat sizes in the gray zone and high end of the normal range are associated with premature ovarian failure

Premature ovarian failure (POF) is the occurrence of menopause before the age of 40 and affects 1% of the female population. Whereas the etiology of POF is largely unexplained, FMR1 premutation carriers are known to be at increased risk of POF compared with the general population. The FMR1 premutation alleles have 55–200 copies of a CGG repeat in the 5 untranslated region of the FMR1 gene. However, functional effects on gene expression may occur even for repeat sizes in what has been considered the normal range. To evaluate the role of the FMR1 repeat in POF, repeat sizes were examined in 53 women with idiopathic POF, 161 control women from the general population, and 21 women with proven fertility at an advanced maternal age. A significant increase in the number of FMR1 alleles between and including 35 and 54 CGG repeats was found in the POF patient population; 15 of 106 (14.2%) POF alleles were between and including 35 and 54 repeats, whereas only 21 of 322 (6.5%) alleles in the general population (P=0.02) and 2 of 42 (4.8%) alleles from women with proven late fertility (P=0.09) were of this size (P=0.01 versus combined controls). The effect was also significant for comparisons of genotype repeat size (repeat size weighted by the relative activity of the two FMR1 alleles) and biallelic mean (average size of the two alleles). These results are clinically relevant and suggest that the FMR1 gene plays a more significant role in the incidence of POF than has previously been thought.     

Allosteric effects of ligands and mutations on poliovirus RNA-dependent RNA polymerase

Protein priming of viral RNA synthesis plays an essential role in the replication of picornavirus RNA. Both poliovirus and coxsackievirus encode a small polypeptide, VPg, which serves as a primer for addition of the first nucleotide during synthesis of both positive and negative strands. This study examined the effects on the VPg uridylylation reaction of the RNA template sequence, the origin of VPg (coxsackievirus or poliovirus), the origin of 3D polymerase (coxsackievirus or poliovirus), the presence and origin of interacting protein 3CD, and the introduction of mutations at specific regions in the poliovirus 3D polymerase. Substantial effects associated with VPg origin were traced to differences in VPg-polymerase interactions. The effects of 3CD proteins and mutations at polymerase-polymerase intermolecular Interface I were most consistent with allosteric effects on the catalytic 3D polymerase molecule. In conclusion, the efficiency and specificity of VPg uridylylation by picornavirus polymerases is greatly influenced by allosteric effects of ligand binding that are likely to be relevant during the viral replicative cycle.     

Interaction between resistance training and flexibility training in healthy young adults

To test the hypothesis that increases in muscle strength and flexibility are developed by specific training programs, 43 healthy young adults were tested before and after 4 different interventions conducted twice a week for 12 weeks: (a) resistance training only (n = 13); (b) flexibility training only (n = 11); (c) resistance and flexibility training (n = 9); and (d) no intervention (n = 10). There was no change in either strength or flexibility in the control group (p > 0.05). Resistance training improved muscle strength either alone (+14%; effect size = 0.53; p < 0.001) or in combination with flexibility training (+16%; effect size = 0.66; p = 0.032), but did not change flexibility (p = 0.610). Flexibility increased with specific training alone (+33%; p < 0.001) or in combination with resistance training (+18%; p < 0.001). In conclusion, in young, healthy subjects, resistance training alone did not increase flexibility, but resistance training did not interfere with the increase in joint range of motion during flexibility training. These results support the concept that specific training should be employed in order to increase either muscle strength or flexibility.     

Ospemifene inhibits the growth of dimethylbenzanthracene-induced mammary tumors in Sencar mice

Ospemifene is a new selective estrogen receptor modulator (SERM) that is being developed for the treatment of urogenital atrophy and osteoporosis. Similarly to other SERMs, ospemifene exhibits antiestrogenic effects in breast tissue, which led to the hypothesis that it may be a potential breast cancer chemopreventive agent. We first assessed the ability of ospemifene, compared to tamoxifen and raloxifene, to prevent dimethylbenzanthracene (DMBA)-induced mammary tumors in female Sencar mice. Ospemifene (N = 18), tamoxifen (N = 20) and raloxifene (N = 17), each dosed at 50 mg/kg, were administered daily by oral gavage, in combination with 20 microg DMBA for the first 6 weeks. Control mice (N = 21) received vehicle plus DMBA only for the first 6 weeks. Daily treatment then continued for 37 weeks. As hypothesized, ospemifene greatly reduced the incidence of mammary carcinomas compared to control mice (p = 0.003), similar to tamoxifen (p = 0.0004); however, in the raloxifene group, no significant effect was seen in mammary tumor prevention (p = 0.20). A follow-up study comparing ospemifene (N = 20) to tamoxifen (N = 20) in the same model was then performed to confirm the results of the first study. The results of the follow-up study, which extended the treatment to 52 weeks, confirmed the results of our previous study, with ospemifene (p = 0.01) and tamoxifen (p = 0.004) significantly decreasing mammary carcinomas compared to controls. The results of these two studies suggest that women taking ospemifene for osteoporosis and/or urogenital atrophy may further benefit from ospemifene's breast cancer chemopreventive effects.     

Molecular Dynamics Simulations of the Periplasmic Ferric-hydroxamate Binding Protein FhuD

FhuD is a periplasmic binding protein (PBP) that, under iron-limiting conditions, transports various hydroxamate-type siderophores from the outer membrane receptor (FhuA) to the inner membrane ATP-binding cassette transporter (FhuBC). Unlike many other PBPs, FhuD possesses two independently folded domains that are connected by an α-helix rather than two or three central β-strands. Crystal structures of FhuD with and without bound gallichrome have provided some insight into the mechanism of siderophore binding as well as suggested a potential mechanism for FhuD binding to FhuB. Since the α-helix connecting the two domains imposes greater rigidity on the structure relative to the β-strands in other ‘classical’ PBPs, these structures reveal no large conformational change upon binding a hydroxamate-type siderophore. Therefore, it is difficult to explain how the inner membrane transporter FhuB can distinguish between ferrichrome-bound and ferrichrome-free FhuD. In the current study, we have employed a 30 ns molecular dynamics simulation of FhuD with its bound siderophore removed to explore the dynamic behavior of FhuD in the substrate-free state. The MD simulation suggests that FhuD is somewhat dynamic with a C-terminal domain closure of 6° upon release of its siderophore. This relatively large motion suggests differences that would allow FhuB to distinguish between ferrichrome-bound and ferrichrome-free FhuD.     

Topology of double-membraned vesicles and the opportunity for non-lytic release of cytoplasm

Infection of mammalian cells with several positive-strand RNA viruses induces double-membraned vesicles whose cytosolic surfaces serve as platforms for viral RNA replication. Our recent publication (Jackson et al. PLoS Biol 2005; 3:861-71) chronicled several similarities between poliovirus-induced membranes and autophagosomes, including induced co-localization of GFP-LC3 and LAMP1. Occasionally, the cytosolic lumen of these structures also contains viral particles; this likely results from wrapping of cytosol, which can contain high viral concentrations late in infection, by newly formed double membranes. Interestingly, RNAi treatment to reduce LC3 or Atg12p concentrations reduced yields of extracellular virus even more than intracellular virus. It is often assumed that exit of non-enveloped viruses such as poliovirus requires cell lysis. However, we hypothesize that autophagosome-like double-membranes, which can become single-membraned upon maturation, provide a long-sought mechanism for the observed non-lytic release of cytoplasmic viruses and possibly other cytoplasmic material resistant to the environment of maturing autophagosomes.     

Molecular models of protein kinase 6 from Plasmodium falciparum

Cyclin-dependent kinases (CDKs) have been identified as potential targets for development of drugs, mainly against cancer. These studies generated a vast library of chemical inhibitors of CDKs, and some of these molecules can also inhibit kinases identified in the Plasmodium falciparum genome. Here we describe structural models for Protein Kinase 6 from P. falciparum (PfPK6) complexed with Roscovitine and Olomoucine. These models show clear structural evidence for differences observed in the inhibition, and may help designing inhibitors for PfPK6 generating new potential drugs against malaria. Figure Ribbon diagram of PfPK6 complexed with a roscovitine and b olomoucine     

The identification of residues that control signal peptidase cleavage fidelity and substrate specificity

Signal peptidase, which removes signal peptides from preproteins, has a substrate specificity for small uncharged residues at -1 (P1) and small or larger aliphatic residues at the -3 (P3) position. Structures of the catalytic domain with a 5S-penem inhibitor and a lipopeptide inhibitor reveal candidate residues that make up the S1 and S3 pockets that bind the P1 and P3 specificity residues of the preprotein substrate. We have used site-directed mutagenesis, mass spectrometric analysis, and in vivo and in vitro activity assays as well as molecular modeling to examine the importance of the substrate pocket residues. Generally, we find that the S1 and S3 binding sites can tolerate changes that are expected to increase or decrease the size of the pocket without large effects on activity. One residue that contributes to the high fidelity of cleavage of signal peptidase is the Ile-144 residue. Changes of the Ile-144 residue to cysteine result in cleavage at multiple sites, as determined by mass spectrometry and Edman sequencing analysis. In addition, we find that signal peptidase is able to cleave after phenylalanine at the -1 residue in a double mutant in which both Ile-86 and Ile-144 were changed to an alanine. Also, alteration of the Ile-144 and Ile-86 residues to the corresponding residues found in the homologous Imp1 protease changes the specificity to promote cleavage following a -1 Asn residue. This work shows that Ile-144 and Ile-86 contribute to the signal peptidase substrate specificity and that Ile-144 is important for the accuracy of the cleavage reaction.     

Impact of vitamin E or selenium deficiency on nematode-induced alterations in murine intestinal function

The effects of deficiencies in the antioxidant nutrients, vitamin E and selenium, on the host response to gastrointestinal nematode infection are unknown. The aim of the study was to determine the effect of antioxidant deficiencies on nematode-induced alterations in intestinal function in mice. BALB/c mice were fed control diets or diets deficient in selenium or vitamin E and the response to a secondary challenge inoculation with Heligmosomoides polygyrus was determined. Egg and worm counts were assessed to determine host resistance. Sections of jejunum were mounted in Ussing chambers to measure changes in permeability, absorption, and secretion, or suspended in organ baths to determine smooth muscle contraction. Both selenium and vitamin E deficient diets reduced resistance to helminth infection. Vitamin E, but not selenium, deficiency prevented nematode-induced decreases in glucose absorption and hyper-contractility of smooth muscle. Thus, vitamin E status is an important factor in the physiological response to intestinal nematode infection and may contribute to antioxidant-dependent protective mechanisms in the small intestine.