Infant feeding in the context of HIV: a qualitative study of health care workers’ knowledge of recommended infant feeding options in Papua New Guinea

Background

Interventions to prevent mother to child transmission of human immunodeficiency virus (HIV) during childbirth and breastfeeding can reduce HIV infections in infants to less than 5% in low and middle income countries. The World Health Organization (WHO) recommends all mothers, regardless of their HIV status, practice exclusive breastfeeding for the first six months of an infant’s life. In line with these recommendations and to protect, promote and support breastfeeding, in 2009 the PNG National Department of Health revised their National HIV infant feeding guidelines, reinforcing the WHO recommendation of exclusive breastfeeding for the first six months followed by the introduction of other food and fluids, while continuing breastfeeding.The overall aim of this paper is to explore health care workers’ knowledge regarding infant feeding options in PNG, specifically as they relate to HIV exposed infants.

Methods

As part of a study investigating women’s and men’s experiences of prevention of mother to child transmission (PMTCT) services in two sites in PNG, 28 key informant interviews were undertaken. This paper addresses one theme that emerged from thematic data analysis: Health care workers’ knowledge regarding infant feeding options, specifically how this knowledge reflects the Papua New Guinea National HIV Care and Treatment Guidelines on HIV and infant feeding (2009).

Results

Most informants mentioned exclusive breastfeeding, the majority of whom reflected the most up-to-date National Guidelines of exclusive breastfeeding for six months. The importance of breastfeeding continuing beyond this time, along with the introduction of food and fluids was less well understood. The most senior people involved in PMTCT were the informants who most accurately reflected the national guidelines of continuing breastfeeding after six months.

Conclusion

Providing advice on optimal infant feeding in resource poor settings is problematic, especially in relation to HIV transmission. Findings from our study reflect those found elsewhere in identifying that key health care workers are not aware of up-to-date information relating to infant feeding, especially within the context of HIV. Greater emphasis needs to be placed on ensuring the most recent feeding guidelines are disseminated and implemented in clinical practice in PNG.

     

Novel O-palmitolylated beta-E1 subunit of pyruvate dehydrogenase is phosphorylated during ischemia/reperfusion injury

Background  

During and following myocardial ischemia, glucose oxidation rates are low and fatty acids dominate as a source of oxidative metabolism. This metabolic phenotype is associated with contractile dysfunction during reperfusion. To determine the mechanism of this reliance on fatty acid oxidation as a source of ATP generation, a functional proteomics approach was utilized.     

Statistical analysis of an RNA titration series evaluates microarray precision and sensitivity on a whole-array basis

Background

It is one of the ultimate goals for modern biological research to fully elucidate the intricate interplays and the regulations of the molecular determinants that propel and characterize the progression of versatile life phenomena, to name a few, cell cycling, developmental biology, aging, and the progressive and recurrent pathogenesis of complex diseases. The vast amount of large-scale and genome-wide time-resolved data is becoming increasing available, which provides the golden opportunity to unravel the challenging reverse-engineering problem of time-delayed gene regulatory networks.

Results

In particular, this methodological paper aims to reconstruct regulatory networks from temporal gene expression data by using delayed correlations between genes, i.e., pairwise overlaps of expression levels shifted in time relative each other. We have thus developed a novel model-free computational toolbox termed TdGRN (Time-delayed Gene Regulatory Network) to address the underlying regulations of genes that can span any unit(s) of time intervals. This bioinformatics toolbox has provided a unified approach to uncovering time trends of gene regulations through decision analysis of the newly designed time-delayed gene expression matrix. We have applied the proposed method to yeast cell cycling and human HeLa cell cycling and have discovered most of the underlying time-delayed regulations that are supported by multiple lines of experimental evidence and that are remarkably consistent with the current knowledge on phase characteristics for the cell cyclings.

Conclusion

We established a usable and powerful model-free approach to dissecting high-order dynamic trends of gene-gene interactions. We have carefully validated the proposed algorithm by applying it to two publicly available cell cycling datasets. In addition to uncovering the time trends of gene regulations for cell cycling, this unified approach can also be used to study the complex gene regulations related to the development, aging and progressive pathogenesis of a complex disease where potential dependences between different experiment units might occurs.     

A nuclear gene for higher level phylogenetics: phosphoenolpyruvate carboxykinase tracks mesozoic-age divergences within Lepidoptera (Insecta)

The sequence of phosphoenolpyruvate carboxykinase (PEPCK) has been previously identified as a promising candidate for reconstructing Mesozoic-age divergences (Friedlander, Regier, and Mitter 1992, 1994). To test this hypothesis more rigorously, 597 nucleotides of aligned PEPCK coding sequence (approximately 30% of the coding region) were generated from 18 species representing Mesozoic-age lineages of moths (Insecta: Lepidoptera) and outgroup taxa. Relationships among basal Lepidoptera are well established by morphological analysis, providing a strong test for the utility of a gene which has not previously been used in systematics. Parsimony and other phylogenetic analyses were conducted on nucleotides by codon positions (nt1, nt2, nt3) separately and in combination, and on amino acids, for comparison to the test phylogeny. The highest concordance was achieved with nt1 + nt2, for which one of two most-parsimonious trees was identical to the test phylogeny, and with all nucleotides when nt3 was down-weighted sevenfold or higher, for which a single most-parsimonious tree identical to the test phylogeny resulted. Substitutions in nt3 approached saturation in many, but not all, pairwise comparisons and their exclusion or severe downweighting greatly increased the degree of concordance with the test phylogeny. Neighbor-joining analysis confirms this finding. The utility of PEPCK for phylogenetics is demonstrated over a time span for which few other suitable genes are currently available.      

Imatinib and Dasatinib Inhibit Hemangiosarcoma and Implicate PDGFR-β and Src in Tumor Growth

Hemangiosarcoma, a natural model of human angiosarcoma, is an aggressive vascular tumor diagnosed commonly in dogs. The documented expression of several receptor tyrosine kinases (RTKs) by these tumors makes them attractive targets for therapeutic intervention using tyrosine kinase inhibitors (TKIs). However, we possess limited knowledge of the effects of TKIs on hemangiosarcoma as well as other soft tissue sarcomas. We report here on the use of the TKIs imatinib and dasatinib in canine hemangiosarcoma and their effects on platelet-derived growth factor receptor β (PDGFR-β) and Src inhibition. Both TKIs reduced cell viability, but dasatinib was markedly more potent in this regard, mediating cytotoxic effects orders of magnitude greater than imatinib. Dasatinib also inhibited the phosphorylation of the shared PDGFR-β target at a concentration approximately 1000 times less than that needed by imatinib and effectively blocked Src phosphorylation. Both inhibitors augmented the response to doxorubicin, suggesting that clinical responses likely will be improved using both drugs in combination; however, dasatinib was significantly (P < .05) more effective in this context. Despite the higher concentrations needed in cell-based assays, imatinib significantly inhibited tumor growth (P < .05) in a tumor xenograft model, highlighting that disruption of PDGFR-β/PDGF signaling may be important in targeting the angiogenic nature of these tumors. Treatment of a dog with spontaneously occurring hemangiosarcoma established that clinically achievable doses of dasatinib may be realized in dogs and provides a means to investigate the effect of TKIs on soft tissue sarcomas in a large animal model.     

Statistical analysis of an RNA titration series evaluates microarray precision and sensitivity on a whole-array basis

Background  

Concerns are often raised about the accuracy of microarray technologies and the degree of cross-platform agreement, but there are yet no methods which can unambiguously evaluate precision and sensitivity for these technologies on a whole-array basis.     

Mechanisms of corticosteroid action on lymphocyte subpopulations: VI. Lack of correlation between glucocorticosteroid receptors and the differential effects of glucocorticosteroids on T-cell subpopulations

Glucocorticosteroid receptors were measured in subpopulations of human peripheral blood T cells identified by the presence of an Fc receptor for IgG (T_G) or an Fc receptor for IgM (T_M). T_M cells are selectively depleted from the circulation by in vivo administration of glucocorticosteroids as opposed to T_G cells which are relatively resistant to the lymphodepletive effects of these hormones. However, this selective lymphodepletive effect of glucocorticosteroids on T_M cells could not be explained on the basis of detectable differences in intracytoplasmic glucocorticosteroid receptors in these T-cell subpopulations since T_G and T_M cells had quantitatively similar glucocorticosteroid receptors as well as remarkably similar dexamethasone binding affinities and dissociation constants. Hence, the strikingly different effects of glucocorticosteroids on the circulatory kinetics of T_G and T_M cells must be explained by mechanisms other than those at the level of the glucocorticosteroid receptor.     

Cortisol production rate measurement by stable isotope dilution using gas chromatography-negative ion chemical ionization mass spectrometry.

Presented here is a stable isotope dilution technique for determining cortisol production rate (CPR). The method involves extraction and derivatization of cortisol isoforms from serum (0.5 ml), separation of derivatives by gas chromatography, and detection by using negative ion chemical ionization mass spectrometry. This method provides 50-100-fold greater sensitivity than positive ion mass spectrometry and allows for estimations of cortisol production rate with the use of small amounts of pooled serum, even in the presence of high concentrations of lipophilic contaminants. The area under the curve for the total selected ion chromatogram of fluoroacyl derivatives of cortisol (d0, m/z 782) and deuterated cortisol (d3, m/z 785) were used to determine the isotopic dilution ratio in three types of samples: 1) standards: d0/d3 ratios ranging from 1 to 8%; 2) controls: d3-cortisol added to serum with known cortisol concentration; 3) subjects: 24-h pooled serum samples (q 30 min over 24 h) from healthy children (male 10-13 years; female 7-11 years) receiving continuous infusions of d3-cortisol at 2-4% of their estimated CPR. Recovery after the solid phase extraction and derivatization process was >90%, as determined by thin-layer chromatography. Expected versus measured ratios for d3/d0 in standards and serum controls were highly correlated (r2(standard) = 0.99; r2(control) = 0.99) over a wide range of d3-cortisol enrichment (1.0-10.0%). Mean 24-h CPRs were 4.8 +/- 0.6 mg/m2/24 h (mean +/- SEM, n = 7) in male children and 4.4 +/- 0.5 mg/m2/24 h in female children (n = 4). These CPR values are lower than those derived by radio tracer methods, but are in agreement with previous isotopic dilution studies. This technique is an important tool for assessing CPRs in a wide range of disease states affecting cortisol production.     

Low plasma levels of 2-hydrdxyestrone are consistent with its rapid metabolic clearance

Published plasma levels of the catechol estrogen 2-hydroxyestrone (2-OHE₁) are comparable to those of estrone and estradiol. In light of the very high (40,000 L/d) metabolic clearance rate of 2-OHEi, these concentrations imply unreasonable production rates. We therefore re-examined plasma 2-OHE₁ levels using a modified radiotnnmmoassay procedure. Plasma samples are extracted with ethyl acetate and passed over a short column of LH-20 Sephadex before equilibration with an antiserum directed against a 2-hydroxyestrone-17-(O-carboxymethyl)oxime-bovine serum albumin conjugate. Plasma 2-OHE₁ concentrations are indistinguishable from blank (< 15 pg/ml) in men and non-pregnant women, but rise to ~ 200 pg/ml during pregnancy. These values for 2-OHE₁ levels are consistent with the rapid metabolic clearance of this catechol estrogen.