Dyspnea in Children with Life-Threatening and Life-Limiting Complex Chronic Conditions.

BACKGROUND: Dyspnea is one of the most frequent symptoms in children with complex chronic conditions (CCC) requiring palliative care. Although it is a subject of high importance, there has been little research on dyspnea in critically ill children. OBJECTIVE: The purpose of this systematic review was to investigate the prevalence and causes of dyspnea in children with CCC and to identify the current state of research on the measurements, treatments, and the evaluation of therapeutic interventions. METHODS: A systematic literature search for relevant literature from 1990 until the present was performed using the online database PubMed. Information about prevalence, pathophysiological mechanisms, measurement, and treatment of dyspnea was extracted from all 43 eligible publications. RESULTS: The prevalence ranged widely from 17% to 80%. Breathlessness was primarily attributed to a disease-specific pathophysiology. A multidimensional approach has not been reported. Assessment of dyspnea included eight tools using either subjective self- or proxy-ratings or objective measures. Evidence for the effectiveness of various treatment approaches was low. DISCUSSION: The prevalence rates for dyspnea could be generalized across all conditions and patient subgroups. The biopsychosocial-spiritual approach was not addressed by the studies. There is a lack of an adequate and validated measurement tool that can be applied to children of various ages and diagnoses, communication ability, and practicable across different settings. Most found treatment approaches lacked good evidence in children. CONCLUSION: Although the prevalence rate of dyspnea in pediatric palliative care is high, it has been poorly studied.

Pyrenylmethyldeoxyadenosine: a 3'-cap for universal DNA hybridization probes.

A ligand that stabilizes a three-dimensional structure can be expected to have a positive effect on the specificity with which this structure is formed. Here we report on a ligand covalently linked to an oligonucleotide that increases duplex stability, but decreases base-pairing selectivity at the terminus. The ligand consists of a dangling 2'-deoxyadenosine residue with a pyrenylmethyl substituent at the N6-position, that is, a deoxynucleoside with a covalently linked polycyclic aromatic hydrocarbon (PAH). In the presence of the pyrene-bearing nucleosides the UV melting point (DeltaT(m)) of duplexes increases by up to 29.1 degrees C. The modified residue lowers the base-pairing fidelity at the terminal and penultimate position of duplexes with a depression in DeltaDeltaT(m) observable in 20 out of 24 sequence contexts tested. The effect can be rationalized based on a modeled three-dimensional structure. The results are significant for the understanding of base-pairing fidelity in DNA duplexes as modulated by the presence of a polycyclic aromatic hydrocarbon. The fidelity-decreasing effect may be useful for universal hybridization probes that bind to a broader range of sequences than conventional oligonucleotides.

Optimizing the stacking moiety and linker of 2'-acylamido caps of DNA duplexes with 3'-terminal adenine residues.

Reported here is the synthesis of oligodeoxynucleotides with a 3'-terminal 2'-acylamido-2'-deoxyadenosine residue. The route to these oligonucleotides employs an N,O-Alloc-protected 5'-phosphoramidite of 2'-amino-2'-deoxyadenosine that was prepared in 11 steps from arabinoadenosine. Small combinatorial libraries of oligonucleotides were generated via acylation with a mixture of linker amino acids and subsequent acylation of their amino groups. Mass spectrometrically monitored nuclease selection assays led to oligonucleotides whose 2'-substituent increases the thermal stability of the DNA duplexes. A linker with three methylene groups between a perylene stacking moiety and the amido group gives a UV-melting point increase of up to 27.9 degrees C for the DNA sequence (TGCGCA*)2, where A* denotes the 2'-acylamidoadenosine residue. The same acylamido group improves mismatch discrimination at the terminal position with a melting point depression of >or=7 degrees C for any of the three mismatches in the target sequence of the octamer 5'-AGGTTGAA-3'. These results demonstrate how even a very weakly base-pairing nucleotide at the 3'-terminus of a DNA probe strand can be enforced to engage in strong and highly sequence-selective base-pairing interactions.

Molecular details of quinolone-DNA interactions: solution structure of an unusually stable DNA duplex with covalently linked nalidixic acid residues and non-covalent complexes derived from it.

Quinolones are antibacterial drugs that are thought to bind preferentially to disturbed regions of DNA. They do not fall into the classical categories of intercalators, groove binders or electrostatic binders to the backbone. We solved the 3D structure of the DNA duplex (ACGCGU-NA)2, where NA denotes a nalidixic acid residue covalently linked to the 2'-position of 2'-amino-2'-deoxyuridine, by NMR and restrained torsion angle molecular dynamics (MD). In the complex, the quinolones stack on G:C base pairs of the core tetramer and disrupt the terminal A:U base pair. The displaced dA residues can stack on the quinolones, while the uracil rings bind in the minor groove. The duplex-bridging interactions of the drugs and the contacts of the displaced nucleotides explain the high UV-melting temperature for d(ACGCGU-NA)2 of up to 53 degrees C. Further, non-covalently linked complexes between quinolones and DNA of the sequence ACGCGT can be generated via MD using constraints obtained for d(ACGCGU-NA)2. This is demonstrated for unconjugated nalidixic acid and its 6-fluoro derivative. The well-ordered and tightly packed structures thus obtained are compatible with a published model for the quinolone-DNA complex in the active site of gyrases.