Fibreoptic bronchoscopy: ten years on.

Fibreoptic bronchoscopy was introduced more than 10 years ago and is now in many centres a routine diagnostic procedure, having superseded rigid bronchoscopy. Its major role is in the diagnosis of bronchial carcinoma, where the results are as good as, if not better than, results with the rigid instrument. Other major applications have been found in investigating haemoptysis, transbronchial lung biopsy in interstitial lung disease, and in the critically ill patient in the intensive care unit. More recently, the instrument has been used to perform bronchoalveolar lavage in investigating interstitial lung diseases and to enable lobar and segmental lung function studies to be performed. Fibreoptic bronchoscopy is a major advance in the diagnosis of pulmonary diseases, but there will always be times when rigid bronchoscopy is preferable.     

Land-use intensification systematically alters the size structure of aquatic communities in the Neotropics

Land-use and land-cover transitions can affect biodiversity and ecosystem functioning in a myriad of ways, including how energy is transferred within food-webs. Size spectra (i.e. relationships between body size and biomass or abundance) provide a means to assess how food-webs respond to environmental stressors by depicting how energy is transferred from small to larger organisms. Here, we investigated changes in the size spectrum of aquatic macroinvertebrates along a broad land-use intensification gradient (from Atlantic Forest to mechanized agriculture) in 30 Brazilian streams. We expected to find a steeper size spectrum slope and lower total biomass in more disturbed streams due to higher energetic expenditure in physiologically stressful conditions, which has a disproportionate impact on large individuals. As expected, we found that more disturbed streams had fewer small organisms than pristine forest streams, but, surprisingly, they had shallower size spectrum slopes, which indicates that energy might be transferred more efficiently in disturbed streams. Disturbed streams were also less taxonomically diverse, suggesting that the potentially higher energy transfer in these webs might be channelled via a few efficient trophic links. However, because total biomass was higher in pristine streams, these sites still supported a greater number of larger organisms and longer food chains (i.e. larger size range). Our results indicate that land-use intensification decreases ecosystem stability and enhances vulnerability to population extinctions by reducing the possible energetic pathways while enhancing efficiency between the remaining food-web linkages. Our study represents a step forward in understanding how land-use intensification affects trophic interactions and ecosystem functioning in aquatic systems.     

Large, rapidly evolving intergenic spacers in the mitochondrial DNA of the salamander family Ambystomatidae (Amphibia: Caudata)

We report the presence, in the mitochondrial DNA (mtDNA) of all of the sexual species of the salamander family Ambystomatidae, of a shared 240- bp intergenic spacer between tRNAThr and tRNAPro. We place the intergenic spacer in context by presenting the sequence of 1,746 bp of mtDNA from Ambystoma tigrinum tigrinum, describe the nucleotide composition of the intergenic spacer in all of the species of Ambystomatidae, and compare it to other coding and noncoding regions of Ambystoma and several other vertebrate mtDNAs. The nucleotide substitution rate of the intergenic spacer is approximately three times faster than the substitution rate of the control region, as shown by comparisons among six Ambystoma macrodactylum sequences and eight members of the Ambystoma tigrinum complex. We also found additional inserts within the intergenic spacers of five species that varied from 87-444 bp in length. The presence of the intergenic spacer in all sexual species of Ambystomatidae suggests that it arose at least 20 MYA and has been a stable component of the ambystomatid mtDNA ever since. As such, it represents one of the few examples of a large and persistent intergenic spacer in the mtDNA of any vertebrate clade.      

TNF-α is associated with loss of lean body mass only in already cachectic COPD patients

Background

Systemic inflammation may contribute to cachexia in patients with chronic obstructive pulmonary disease (COPD). In this longitudinal study we assessed the association between circulating C-reactive protein (CRP), tumor necrosis factor (TNF)-α, interleukin (IL)-1ß, and IL-6 levels and subsequent loss of fat free mass and fat mass in more than 400 COPD patients over three years.

Methods

The patients, aged 40–76, GOLD stage II-IV, were enrolled in 2006/07, and followed annually. Fat free mass and fat mass indexes (FFMI & FMI) were calculated using bioelectrical impedance, and CRP, TNF-α, IL-1ß, and IL-6 were measured using enzyme immunoassays. Associations with mean change in FFMI and FMI of the four inflammatory plasma markers, sex, age, smoking, FEV₁, inhaled steroids, arterial hypoxemia, and Charlson comorbidity score were analyzed with linear mixed models.

Results

At baseline, only CRP was significantly (but weakly) associated with FFMI (r = 0.18, p < 0.01) and FMI (r = 0.27, p < 0.01). Univariately, higher age, lower FEV₁, and use of beta2-agonists were the only significant predictors of decline in FFMI, whereas smoking, hypoxemia, Charlson score, and use of inhaled steroids predicted increased loss in FMI. Multivariately, high levels of TNF-α (but not CRP, IL-1ß or IL-6) significantly predicted loss of FFMI, however only in patients with established cachexia at entry.

Conclusion

This study does not support the hypothesis that systemic inflammation is the cause of accelerated loss of fat free mass in COPD patients, but suggests a role for TNF-α in already cachectic COPD patients.     

An aetiological study of 290 XXY males,with special reference to the role of paternal age

Summary Data on 290 non-mosaic 47,XXY males have been analysed for possible associations with parental ages at birth, season of birth, sex ratio among sibs, and twinning. Comparison with matched population controls revealed a highly significant association with parental age, which was fully explained by dependence on maternal age and maternal age alone. The maternal age effect was determined with greater precision than in an earlier study of the same material, in which siblings were used as controls, and was estimated to result in an increased risk of between 5% and 10% per annum (p.a.). The estimated independent effect of paternal age, after fitting maternal age, was marginally (but not significantly) negative, and excluded an increased risk in excess of 3% p.a. Paternal age therefore appears to have little if any independent significance in the aetiology of 47,XXY. After correcting for seasonal variations in the population birth rate and smoothing, there was a peak of XXY births in March and a trough in November. Though not statistically significant, the pattern resembled that reported in previous studies, and was similar for both younger and older mothers. The twinning rate for both the XXYs and their sibs, and the sex ratio among the latter, were close to the corresponding population values.     

Differential response of cycling and noncycling cells to inducers of DNA synthesis and mitosis

The objective of this study was to determine whether cells in G(0) phase are functionally distinct from those in G(1) with regard to their ability to respond to the inducers of DNA synthesis and to retard the cell cycle traverse of the G(2) component after fusion. Synchronized populations of HeLa cells in G(1) and human diploid fibroblasts in G(1) and G(0) phases were separately fused using UV-inactivated Sendai virus with HeLa cells prelabeled with [(3)H]ThdR and synchronized in S or G(2) phases. The kinetics of initiation of DNA synthesis in the nuclei of G(0) and G(1) cells residing in G(0)/S and G(1)/S dikaryons, respectively, were studied as a function of time after fusion. In the G(0)/G(2) and G(1)/G(2) fusions, the rate of entry into mitosis of the heterophasic binucleate cells was monitored in the presence of Colcemid. The effects of protein synthesis inhibition in the G(1) cells, and the UV irradiation of G(0) cells before fusion, on the rate of entry of the G(2) component into mitosis were also studied. The results of this study indicate that DNA synthesis can be induced in G(0)nuclei after fusion between G(0)- and S-phase cells, but G(0) nuclei are much slower than G(1) nuclei in responding to the inducers of DNA synthesis because the chromatin of G(0) cells is more condensed than it is in G(1) cells. A more interesting observation resulting from this study is that G(0) cells is more condensed than it is in G(1) cells. A more interesting observation resulting from this study is that G(0) cells differ from G(1) cells with regard to their effects on the cell cycle progression of the G(2) nucleus into mitosis. This difference between G(0) and G(1) cells appears to depend on certain factors, probably nonhistone proteins, present in G(1) cells but absent in G(0) cells. These factors can be induced in G(0) cells by UV irradiation and inhibited in G(1) cells by cycloheximide treatment.     

Alpha-B crystallin gene (CRYAB) mutation causes dominant congenital posterior polar cataract in humans

Congenital cataracts are an important cause of bilateral visual impairment in infants. In a four-generation family of English descent, we mapped dominant congenital posterior polar cataract to chromosome 11q22-q22.3. The maximum LOD score, 3.92 at recombination fraction 0, was obtained for marker D11S898, near the gene that encodes crystallin alpha-B protein (CRYAB). By sequencing the coding regions of CRYAB, we found in exon 3 a deletion mutation, 450delA, that is associated with cataract in this family. The mutation resulted in a frameshift in codon 150 and produced an aberrant protein consisting of 184 residues. This is the first report of a mutation, in this gene, resulting in isolated congenital cataract.     

Crystal structure of the topoisomerase II poison 9-amino-[N-(2-dimethylamino)ethyl]acridine-4-carboxamide bound to the DNA hexanucleotide d(CGTACG)2.

The structure of the complex formed between d(CGTACG)(2) and the antitumor agent 9-amino-[N-(2-dimethylamino)ethyl]acridine-4-carboxamide has been solved to a resolution of 1.6 A using X-ray crystallography. The complex crystallized in space group P6(4) with unit cell dimensions a = b = 30.2 A and c = 39.7 A, alpha = beta = 90 degrees, gamma = 120 degrees. The asymmetric unit contains a single strand of DNA, 1. 5 drug molecules, and 29 water molecules. The final structure has an overall R factor of 19.3%. A drug molecule intercalates between each of the CpG dinucleotide steps with its side chain lying in the major groove, and the protonated dimethylamino group partially occupies positions close to ( approximately 3.0 A) the N7 and O6 atoms of guanine G2. A water molecule forms bridging hydrogen bonds between the 4-carboxamide NH and the phosphate group of the same guanine. Sugar rings adopt the C2'-endo conformation except for cytosine C1 which moves to C3'-endo, thereby preventing steric collision between its C2' methylene group and the intercalated acridine ring. The intercalation cavity is opened by rotations of the main chain torsion angles alpha and gamma at guanines G2 and G6. Intercalation perturbs helix winding throughout the hexanucleotide compared to B-DNA, steps 1 and 2 being unwound by 8 degrees and 12 degrees, respectively, whereas the central TpA step is overwound by 17 degrees. An additional drug molecule, lying with the 2-fold axis in the plane of the acridine ring, is located at the end of each DNA helix, linking it to the next duplex to form a continuously stacked structure. The protonated N,N-dimethylamino group of this "end-stacked" drug hydrogen bonds to the N7 atom of guanine G6. In both drug molecules, the 4-carboxamide group is internally hydrogen bonded to the protonated N-10 atom of the acridine ring. The structure of the intercalated complex enables a rationalization of the known structure-activity relationships for inhibition of topoisomerase II activity, cytotoxicity, and DNA-binding kinetics for 9-aminoacridine-4-carboxamides.