Is the partial pressure of carbon dioxide in the blood related to the development of retinopathy of prematurity?

AIMS—To determine the role of carbon dioxide in the development of retinopathy of prematurity (ROP).
METHODS—This was a retrospective cohort study of 25 consecutive infants admitted to the neonatal unit with continuously recorded physiological data. The daily mean and standard deviation (SD) of transcutaneous carbon dioxide partial pressure (tcPCO(2)) was compared between infants who had stage 1 or 2 ROP and stage 3 ROP. The time spent hypocarbic (<3 kPa) and/or hypercarbic (>10 kPa and >12 kPa) was also compared between these groups. Intermittent arterial carbon dioxide tension was also measured and compared with the simultaneous tcPCO(2) data.
RESULTS—There were no significant differences in carbon dioxide variability or time spent hypocarbic and/or hypercarbic between the ROP groups on any day. 86% of transcutaneous values were within 1.5 kPa of the simultaneous arterial value.
CONCLUSION—TcPCO(2) measurement can be a very useful management technique. However, in this cohort neither variable blood carbon dioxide tension nor duration of hypercarbia or hypocarbia in the first 2 weeks of life was associated with the development or severity of ROP.


Effect of high versus low initial doses of L-thyroxine for congenital hypothyroidism on thyroid function and somatic growth

&lt;p&gt;&lt;b&gt;Background and aims:&lt;/b&gt; The optimal dose of thyroxine (T4) in congenital hypothyroidism (CH) during infancy is controversial. Higher doses lead to improvement in cognitive scores, but have been linked to later behavioural difficulties. We have examined the effects of initial T4 dosage on somatic growth - a putative surrogate marker of overtreatment.&lt;/p&gt; &lt;p&gt;&lt;b&gt;Methods:&lt;/b&gt; 314 CH children (214 girls, 100 boys) were analysed according to initial daily dose of T4: Group 1 (25 μgg, n=152), Group 2 (30-40μgg, n=63) and Group 3 (50 μgg , n=99). Thyroid function and weight, length and occipito-frontal head circumference (OFC) SDS were compared at 3, 6, 12, 18, 24 and 36 months of age. Linear growth SDS was compared between the three groups using a regression adjustment model at 12 and 18 months of age using birth weight and 3 month data as baselines. Thyroid function was also compared at diagnosis (T0), and 7-21 days after the start of treatment (T1).&lt;/p&gt; &lt;p&gt;&lt;b&gt;Results:&lt;/b&gt; At T1 median TSH for Groups 1, 2 and 3 was 58, 29 and 4.1 mU/L respectively (p &#60;0.001), Group 3 values remaining significantly lower at 3 and 6 months. Median fT4 was within or just above the reference range in all groups at T1, but 7.4% of Group 1 had values &#60; 9 pmol/L compared with 5.1% and 0% for Groups 2 and 3 respectively. At 3 months weight, length and OFC SDS values were -0.39, -0.35, 0.09; -0.30, -0.47, 0.32; and -0.03, -0.13, 0.18 for Groups 1, 2 and 3 respectively, indicating relatively large OFC in all infants. A regression adjustment model showed no significant difference in growth rate from baseline and 12 or 18 months of age between the three groups.&lt;/p&gt; &lt;p&gt;&lt;b&gt;Conclusion:&lt;/b&gt; An initial T4 dose of 50 μgg daily normalises thyroid function several months earlier than lower dose regimes, with no evidence of sustained somatic overgrowth between 3 months and 3 years.&lt;/p&gt

Model for a transcript map of human chromosome 21: isolation of new coding sequences from exon and enriched cDNA libraries.

The construction of a transcriptional map for human chromosome 21 requires the generation of a specific catalogue of genes, together with corresponding mapping information. Towards this goal, we conducted a pilot study on a pool of random chromosome 21 cosmids representing 2 Mb of non-contiguous DNA. Exon-amplification and cDNA selection methods were used in combination to extract the coding content from these cosmids, and to derive expressed sequences libraries. These libraries and the source cosmid library were arrayed at high density for hybridisation screening. A strategy was used which related data obtained by multiple hybridisations of clones originating from one library, screened against the other libraries. In this way, it was possible to integrate the information with the physical map and to compare the gene recovery rate of each technique. cDNAs and exons were grouped into bins delineated by EcoRI cosmid fragments, and a subset of 91 cDNAs and 29 exons have been sequenced. These sequences defined 79 non-overlapping potential coding segments distributed in 24 transcriptional units, which were mapped along 21q. Northern blot analysis performed for a subset of cDNAs indicated the existence of a cognate transcript. Comparison to databases indicated three segments matching to known chromosome 21 genes: PFKL, COL6A1 and S100B and six segments matching to unmapped anonymous expressed sequence tags (ESTs). At the translated nucleotide level, strong homologies to known proteins were found with ATP-binding transporters of the ABC family and the dihydroorotase domain of pyrimidine synthetases. These data strongly suggest that bona fide partial genes have been isolated. Several of the newly isolated transcriptional units map to clinically important regions, in particular those involved in Down's syndrome, progressive myoclonus epilepsia and auto-immune polyglandular disease. The study presented here illustrates the complementarity of exon-amplification and cDNA selection techniques for generating a large resource of new expressed landmarks, which contribute to the construction of a chromosome 21 transcript map

Construction, arraying, and high-density screening of large insert libraries of human chromosomes X and 21: their potential use as reference libraries.

We have constructed cosmid libraries from flow-sorted human chromosomes X and 21, each of which contains greater than 30 genome equivalents, and have developed systems allowing permanent storage of primary clones, easy screening of libraries in high-density filter formats, and the simultaneous generation of fingerprinting and mapping data on the same set of cosmid clones. Clones are picked into microtiter plate wells and stored at -70 degrees C. A semiautomatic robot system allows the generation of filter replicas containing up to 10,000 clones per membrane. Sets of membranes containing 15-20 chromosome equivalents of both chromosomes will be used for the construction of ordered clone libraries by hybridization fingerprinting protocols. In addition, multiple sets of two membranes containing 4 chromosome equivalents of the human X chromosome, and one membrane containing 3 chromosome equivalents of chromosome 21, have been distributed to other interested laboratories as part of a system of reference libraries. This system allows other groups easy access to the clones and offers an efficient protocol to combine results generated in different laboratories using these libraries. Here we describe the construction of the libraries and demonstrate the use of high-density screening filters in oligonucleotide probe hybridizations and the isolation of cosmids by hybridization with probes from the X chromosome

Probing Homogeneous Line Broadening in CdSe Nanocrystals Using Multidimensional Electronic Spectroscopy

The finite spectral line width of an ensemble of CdSe nanocrystals arises from size and shape inhomogeneity and the single-nanocrystal spectrum itself. This line width directly limits the performance of nanocrystal-based devices, yet most optical measurements cannot resolve the underlying contributions. We use two-dimensional electronic spectroscopy (2D ES) to measure the line width of the band-edge exciton of CdSe nanocrystals as a function of radii and surface chemistry. We find that the homogeneous width decreases for increasing nanocrystal radius and that surface chemistry plays a critical role in controlling this line width. To explore the hypothesis that unpassivated trap states serve to broaden the homogeneous line width and to explain its size-dependence, we use 3D ES to identify the spectral signatures of exciton–phonon coupling to optical and acoustic phonons. We find enhanced coupling to optical phonon modes for nanocrystals that lack electron-passivating ligands, suggesting that localized surface charges enhance exciton–phonon coupling via the Fröhlich interaction. Lastly, the data reveal that spectral diffusion contributes negligibly to the homogeneous line width on subnanosecond time scales

Beneficial effects of endurance exercise training on skeletal muscle microvasculature in sickle cell disease patients

Epub ahead of printSickle cell disease (SCD) is a genetic hemoglobinopathy leading to two major clinical manifestations: severe chronic hemolytic anemia and iterative vaso-occlusive crises. SCD is also accompanied by profound muscle microvascular remodeling. The beneficial effects of endurance training on microvasculature are widely known. The aim of this study was to evaluate the effects of an endurance training program on microvasculature of skeletal muscle in SCD patients. A biopsy of the vastus lateralis muscle and submaximal incremental exercise were performed before and after the training period. Of the forty randomized SCD patients, complete data sets from 32 were obtained. The training group (n=15) followed a personalized moderate-intensity endurance training program, while the non-training (n=17) group maintained a normal lifestyle. Training consisted of three 40-minute cycle ergometer exercise sessions per week for 8 weeks. Histological analysis highlighted microvascular benefits in the training SCD patients compared to non-training patients, including increases in capillary density (CD) (P = .003), number of capillaries around a fiber (CAF) (P = .015) and functional exchange surface (LC/PF) (P < .0001). Conversely, no significant between-group difference was found in the morphology of capillaries. Indexes of physical ability also improved in the training patients. The moderate-intensity endurance exercise training program improved the muscle capillary network and partly reversed the microvascular defects commonly observed in skeletal muscle of SCD patients. This trial was registered at www.clinicaltrials.gov as #NCT02571088