HIV-related enteropathy in Zambia: a clinical, microbiological, and histological study

To investigate the etiology of chronic diarrhea associated with human immunodeficiency virus (HIV) infection in Lusaka, we studied 63 HIV-positive patients and 36 seronegative controls clinically and endoscopically. Stools were studied for morphology and for opportunist infections. Fifty-five percent of patients seropositive for HIV who presented with a history of chronic diarrhea had parasites; the most common were Cryptosporidium (32%), Isospora belli (16%), and Strongyloides stercoralis (6%). As indicated by villous blunting and inflammation on duodenal histology, those with diarrhea and parasites showed the most severe damage. We could not implicate mycobacteria or bacterial overgrowth as causes for the enteropathy associated with HIV.     

Molecular Epidemiology of Influenza A(H1N1)pdm09 Virus among Humans and Swine,Sri Lanka

After multiple discrete introductions of influenza A(H1N1)pdm09 virus into Sri Lanka, the virus was transmitted among humans, then swine. The spread of virus between geographically distant swine farms is consistent with virus dispersal associated with a vehicle used for swine transportation, although this remains unproven.     

Measurement of Cancer Health Literacy and Identification of Patients with Limited Cancer Health Literacy

Health literacy is related to a broad range of health outcomes. This study was designed to develop a psychometrically sound instrument designed to measure cancer health literacy along a continuum (CHLT-30), to develop another instrument designed to determine whether a patient has limited cancer health literacy (CHLT-6), and to estimate the prevalence of limited cancer health literacy. The Cancer Health Literacy Study involving 1,306 Black and White cancer patients was conducted between April 2011 and April 2013 in the Virginia Commonwealth University Massey Cancer Center and surrounding oncology clinics. A continuous latent variable modeling framework was adopted to dimensionally represent cancer health literacy, whereas discrete latent variable modeling was used to estimate the prevalence rates of limited cancer health literacy. Self confidence about engaging in health decisions was used as the primary outcome in external validation of new instruments. Results from a comprehensive analysis strongly supported the construct validity and reliability of the CHLT-30 and CHLT-6. For both instruments, measurement invariance tests ruled out item/test bias to explain gender and race/ethnicity differences in test scores. The limited cancer health literacy rate was 18%, a subpopulation consisting of overrepresented Black, undereducated, and low-income cancer patients. Overall, the results supported the conclusion that the CHLT-30 accurately measures cancer health literacy along a continuum and that the CHLT-6 efficiently identifies patients with limited cancer health literacy with high accuracy.     

Breast Cancer Diagnosis from Screening in Trinidad and Tobago: Opportunities for Cancer Prevention

Trinidad and Tobago (TT) experiences the highest breast cancer mortality in the Caribbean; the distribution of traditional breast cancer risk factors in this population has not been analyzed. Data on women who underwent breast cancer screening at the TT Cancer Society between January 2009–December 2011(N = 2,689) were retrospectively collected. The screening detected 131 incident breast cancers; variables significantly associated with breast cancer diagnosis were, a positive family history of breast cancer (adjusted odds ratio [OR_adj]: 1.55; 95 % CI 1.00–2.41), presence of symptoms (OR_adj: 1.91; 95 % CI 1.25–2.92), and previous breast surgery (OR_adj: 1.67; 95 % CI 0.97–2.88). Breast cancer was significantly associated with increased breast density. Among healthy women, breast density was positively associated with nulliparity (OR_adj: 1.46, 1.37, 2.52 respectively for density level 2, 3 and 4 vs. 1) and previous breast surgeries (OR_adj: 2.27, 3.09 and 4.13 respectively for density level 2, 3 and 4 vs. 1). This analysis confirms that breast density is an important predictor of newly diagnosed breast cancer in this Caribbean population. Screening is still a diagnostic tool rather than a preventive measure in TT.     

Resident participation and postoperative outcomes in adrenal surgery

Background

The changing paradigm of surgical residency training has raised concerns about the effects on the quality of training. The purpose of this study is to identify if resident participation in laparoscopic adrenalectomy (LA) and open adrenalectomy (OA) cases is associated with deleterious outcomes.

Materials and methods

This is a retrospective study using the American College of Surgeons National Surgical Quality Improvement Program database. Data from patients undergoing LA and OA from 2005 to 2010 were queried. Preoperative variables as well as intra- and post-operative outcomes for each procedure were evaluated. Multivariate logistic regression was used to analyze if resident participation was associated with significant differences in outcomes, compared with no resident participation. Subset analysis was done to determine possible differences in outcomes based on the level of resident participating, divided into junior (Post Graduate Year [PGY]1–3), senior (PGY4–5), or fellow (≥PGY6) levels.

Results

A total of 3219 adrenalectomies were performed. Of these, 735 (22.8%) were OAs and 2484 (77.2%) were LAs. Residents were involved in 2582 (80.2%) surgeries, which comprised 1985 (76.9%) LAs and 597 (23.1%) OAs. Senior residents or fellows performed majority of the cases (85.2%). Mean operative time was significantly higher with resident participation in LA (P < 0.0001) and OA group (P < 0.0001). On multivariate analysis, resident participation was not associated with significant differences in the operative outcomes of 30-d mortality or postoperative complications after laparoscopic or OA.

Conclusions

Although resident participation does increase operative time in LA and OA, this does not appear to be clinically significant and does not result in adverse patient outcomes.     

Molecular mechanisms for the regulation of histone mRNA stem-loop–binding protein by phosphorylation

Replication-dependent histone mRNAs end with a conserved stem loop that is recognized by stem-loop–binding protein (SLBP). The minimal RNA-processing domain of SLBP is phosphorylated at an internal threonine, and Drosophila SLBP (dSLBP) also is phosphorylated at four serines in its 18-aa C-terminal tail. We show that phosphorylation of dSLBP increases RNA-binding affinity dramatically, and we use structural and biophysical analyses of dSLBP and a crystal structure of human SLBP phosphorylated on the internal threonine to understand the striking improvement in RNA binding. Together these results suggest that, although the C-terminal tail of dSLBP does not contact the RNA, phosphorylation of the tail promotes SLBP conformations competent for RNA binding and thereby appears to reduce the entropic penalty for the association. Increased negative charge in this C-terminal tail balances positively charged residues, allowing a more compact ensemble of structures in the absence of RNA.Histone synthesis increases at the beginning of S-phase to package newly replicated DNA with histone proteins, but synthesis must be shut down rapidly and histone mRNA degraded at the end of DNA replication because of the toxicity of surplus histone proteins (1, 2). This cyclic demand for histones requires strict regulation, which is achieved mainly by controlling the synthesis and degradation of histone mRNA (3). Replication-dependent histone mRNAs are the only known cellular mRNAs that are not polyadenylated and instead end with a conserved stem loop (4). Histone mRNAs are generated from longer histone pre-mRNAs as a result of an endonucleolytic cleavage between the stem loop and a purine-rich downstream sequence termed the “histone downstream element” (HDE) (5).Stem-loop–binding protein (SLBP), also known as “hairpin-binding protein” (6), binds to the histone mRNA stem loop, and U7 small nuclear ribonucleoprotein binds to the HDE (7). Other factors, including the endonuclease CPSF-73, are involved in both polyadenylation and histone mRNA 3′-end processing (8–11). In mammalian nuclear extracts, SLBP is not absolutely required for the biochemical reaction of processing (12). In contrast, cleavage of histone pre-mRNA in Drosophila cells and nuclear extracts requires the binding of SLBP to the stem loop (10, 13).The minimal histone mRNA processing domain of Drosophila SLBP contains a 72-aa RNA-binding domain (RBD) unique to SLBPs and an 18-aa C-terminal region (Fig. 1A) (14). This RNA-processing domain (RPD) is necessary and sufficient for histone mRNA 3′-end processing in vitro (15). The RBDs of human SLBP (hSLBP) and Drosophila SLBP (dSLBP) are phosphorylated at a Thr residue in a conserved TPNK motif (16, 17). The recent crystal structure of hSLBP RBD in complex with histone mRNA stem loop and 3′ hExo, a 3′–5′ exonuclease required for histone mRNA degradation, provided the first molecular insights into the architecture of this complex, and revealed how the hSLBP RBD forms a new RNA-binding motif to interact with the stem-loop RNA (18). On the other hand, how SLBP alone interacts with the RNA or how this interaction might be affected by phosphorylation of the TPNK motif is not known.Open in a separate windowFig. 1.Schematic of the domain architecture of dSLBP (Upper) and amino acid sequence alignment of RPDs of Drosophila and human SLBP (Lower). Domains of SLBP include the N-terminal domain (NTD), RBD, and C-terminal region (C). Amino acid sequences are shown with the RBD sequence in the top two rows and the C-terminal region in the bottom row. T230 in the TPNK motif and phosphorylation sites in the C-terminal region are indicated with boldface and asterisks, respectively; the residues involved in RNA binding are shown in cyan; and acidic residues in the C-terminal region are shown in red.The C-terminal region of dSLBP contains a motif, SNSDSDSD, whose hyperphosphorylation is required for efficient processing of histone pre-mRNA (15). Despite the similarity of hSLBP and dSLBP RBDs (55% identical residues) and their ability to bind identical stem-loop RNA sequences, neither SLBP can substitute for the other to process histone pre-mRNA in nuclear extracts; in fact, hSLBP inhibits processing of Drosophila histone pre-mRNA (15). This incompatibility results from differences in the C-terminal region (Fig. 1). The sequence C-terminal to the RBD in hSLBP is required for processing, but it is longer, has no similarity to the Drosophila sequence, and lacks phosphorylation sites.Here we focused on dSLBP and showed that phosphorylation greatly increases dSLBP binding affinity for the histone mRNA stem loop. Mimicking phosphorylation of the dSLBP RPD by mutation of phosphorylation sites to Glu residues at both the TPNK motif and the C-terminal region also boosted binding affinity relative to the nonphosphorylated dSLBP RPD. Structural studies of both the human and Drosophila SLBP RPD indicated that phosphorylation of the TPNK motif stabilizes the RNA-binding domain, but the C-terminal region is flexible in the protein:RNA complex and does not contact the RNA. Instead, we show that the increased negative charge in the C-terminal region of the dSLBP RPD results in a more compact ensemble of protein conformations in the absence of RNA, thereby increasing RNA-binding affinity by reducing the entropy of the unbound protein.