Darwinian selection for sites of Asn-linked glycosylation in phylogenetically disparate eukaryotes and viruses

Numerous protists and rare fungi have truncated Asn-linked glycan precursors and lack N-glycan-dependent quality control (QC) systems for glycoprotein folding in the endoplasmic reticulum. Here, we show that the abundance of sequons (NXT or NXS), which are sites for N-glycosylation of secreted and membrane proteins, varies by more than a factor of 4 among phylogenetically diverse eukaryotes, based on a few variables. There is positive correlation between the density of sequons and the AT content of coding regions, although no causality can be inferred. In contrast, there appears to be Darwinian selection for sequons containing Thr, but not Ser, in eukaryotes that have N-glycan-dependent QC systems. Selection for sequons with Thr, which nearly doubles the sequon density in human secreted and membrane proteins, occurs by an increased conditional probability that Asn and Thr are present in sequons rather than elsewhere. Increasing sequon densities of the hemagglutinin (HA) of influenza viruses A/H3N2 and A/H1N1 during the past few decades of human infection also result from an increased conditional probability that Asn, Thr, and Ser are present in sequons rather than elsewhere. In contrast, there is no selection on sequons by this mechanism in HA of A/H5N1 or 2009 A/H1N1 (Swine flu). Very strong selection for sequons with both Thr and Ser in glycoprotein of M_r 120,000 (gp120) of HIV and related retroviruses results from this same mechanism, as well as amino acid composition bias and increases in AT content. We conclude that there is Darwinian selection for sequons in phylogenetically disparate eukaryotes and viruses.     

CDw60 glycolipid antigens of human leukocytes: structural characterization and cellular distribution

Monoclonal CDw60 antibodies recognize glycolipid antigens with restricted surface expression on human leukocytes. They allow us to define new functional subpopulations of T lymphocytes and are able to induce costimulatory signals. In this report, we describe the molecular composition of CDw60 glycolipid antigens derived from different human leukocyte subpopulations. The glycolipids were isolated and their structures were identified by immunochemical methods. All molecules containing the CDw60 determinant were found in the disialoganglioside fraction. They were O-acetylated derivatives of the gangliosides II3 (Neu5Ac)2-LacCer (GD3), IV3 (Neu5Ac)2-nLc4Cer (DSPG), and VI3 (Neu5Ac)2- nLc6Cer (DSnHC), respectively. The most common CDw60 glycolipid antigen in human leukocytes was 9-O-acetyl GD3. In a comparison of various cell types, the highest concentration of 9-O-acetyl GD3 on a per cell basis was determined in granulocytes and in blood T lymphocytes, whereas B lymphocytes, thymus cells, and monocytes contained considerably smaller amounts of this molecule. Polar CDw60 antigens such as 9-O-acetyl DSPG and 9-O-acetyl DSnHC were only detected in granulocytes.     

Induction of advanced glycation end products and alterations of the tensile properties of articular cartilage

OBJECTIVE: To determine whether increasing advanced glycation end products (AGEs) in bovine articular cartilage to levels present in aged human cartilage modulates the tensile biomechanical properties of the tissue. METHODS: Adult bovine articular cartilage samples were incubated in a buffer solution with ribose to induce the formation of AGEs or in a control solution. Portions of cartilage samples were assayed for biochemical indices of AGEs and tested to assess their tensile biomechanical properties, including stiffness, strength, and elongation at failure. RESULTS: Ribose treatment of cartilage induced increases in tissue fluorescence, absorbance, and pentosidine content (P < 0.001 for each comparison) by amounts similar to those that occur during aging in humans. Ribose treatment of cartilage also induced an increase in dynamic modulus (60% increase) and strength (35% increase), and a decrease (25% decrease) in strain (P < 0.001 for each comparison). CONCLUSION: The concomitant increase in AGEs and alteration of tensile properties of cartilage after ribose treatment suggest that aging-associated changes in AGEs have functional consequences for this tissue. The AGE-associated increases in strength and stiffness of cartilage may be beneficial by counteracting the decreases in these properties that are associated with degeneration. Conversely, the AGE-associated decrease in failure length, or increase in brittleness, together with increased stiffness may predispose cartilage to increased stress concentration, fracture, and aging-associated biomechanical dysfunction.     

Pica during pregnancy among Mexican‐born women: a formative study

Although pica, the craving and purposive consumption of non‐food substances, is common among many populations, especially during pregnancy, the health consequences are not well understood. Further, very little is known about pica among Mexican populations in the United States and Mexico. Therefore, we conducted formative research to understand pica in this understudied population. Our objectives were to identify the frequency and types of pica behaviours, to understand perceived aetiologies and consequences of pica and to ascertain if the behaviour was common enough to warrant a larger study. We held nine focus group discussions (three in the Salinas Valley, California; six in Xoxocotla, Morelos, Mexico) with 76 Mexican‐born women who were currently pregnant or had delivered within the past 2 years. Earth, adobe, bean stones and ice were the most commonly reported pica substances. Twenty‐eight of the 76 participants (37%) reported ever engaging in pica; 22 participants (29%) reported doing so during pregnancy. The proportion of women reporting pica in the United States and Mexico was 43% and 34%, respectively. Women attributed pica to the overwhelming organoleptic appeal of pica substances (especially smell and texture) and to micronutrient deficiencies. Perceived consequences of unfulfilled pica cravings were birthmarks or fetal loss; fulfilled pica cravings were also thought to be generally harmful to the mother or child, with several women specifying toxic lead, pesticides or ‘worms’. In sum, pica among Mexican women is common enough to warrant a larger epidemiologic study of its sociodemographic correlates and physiological consequences.     

A qualitative study exploring parents’ experiences with epinephrine use for their child’s anaphylactic reaction

Background

Children with life threatening food allergies live with the constant threat of a fatal reaction, and caregivers must always be prepared to treat with an epinephrine auto-injector (EAI). This interpretive phenomenological study explored parents’ perceptions and lived experiences with prescribed EAI use for their child.

Methods

The purposive sample included ten parents of five children under 12 years of age, diagnosed with a food allergy and prescribed with an EAI who recently experienced anaphylaxis. Data sources included digitally-recorded semi-structured interviews and a reflexive journal.

Results

Eight main themes emerged: perception of anaphylaxis, life challenges, isolation, anxiety, hesitation, guilt, influence of health care professionals, and lessons learned. Parents uniformly described multiple life challenges and feelings of isolation, anxiety and hesitation during a reaction that lead to subsequent guilt.

Conclusions

Handling reactions correctly provided parents with confidence to treat subsequent reactions. Witnessing the effects of an EAI and receiving positive feedback from health care providers further strengthened their confidence to quickly and competently intervene in future reactions.

     

Quality of life after repair of tetralogy of Fallot

OBJECTIVE: To determine the quality of life in individuals with corrected tetralogy of Fallot. METHODS AND SUBJECTS: Questionnaires concerning quality of life were sent to all 87 surviving patients aged between 16 and 40 years who had undergone intracardiac repair of tetralogy of Fallot and follow-up in the Wessex Cardiothoracic Unit, and to 87 age and sex matched controls, with medically treated haemodynamically insignificant ventricular septal defects. RESULTS: The only significant difference found between the cases and controls was in requirements for schooling, where those with tetralogy of Fallot were more likely to require additional educational help at school (p = 0.044). For all other aspects of quality of life examined by the questionnaire, including social and genetic history, exercise ability, and health related quality of life, no significant differences were found. Different operative techniques, such as transjunctional patching, right ventriculotomy, and previous palliative shunting, did not affect the quality of life of our population with Tetralogy of Fallot, on average twenty years after their surgery, although the range of operative techniques was limited. Neither age at surgery, nor time since surgery, was correlated with measurements of quality of life. CONCLUSIONS: Those who have undergone surgical correction of tetralogy of Fallot have a normal quality of life, with few differences compared to controls.     

Permanent neonatal diabetes due to paternal germline mosaicism for an activating mutation of the KCNJ11 Gene encoding the Kir6.2 subunit of the beta-cell potassium adenosine triphosphate channel

Activating mutations in the KCNJ11 gene encoding for the Kir6.2 subunit of the beta-cell ATP-sensitive potassium channel have recently been shown to be a common cause of permanent neonatal diabetes. In 80% of probands, these are isolated cases resulting from de novo mutations. We describe a family in which two affected paternal half-siblings were found to be heterozygous for the previously reported R201C mutation. Direct sequencing of leukocyte DNA showed that their clinically unaffected mothers and father were genotypically normal. Quantitative real-time PCR analysis of the father's leukocyte DNA detected no trace of mutant DNA. These results are consistent with the father being a mosaic for the mutation, which is restricted to his germline. This is the first report of germline mosaicism in any form of monogenic diabetes. The high percentage of permanent neonatal diabetes cases due to de novo KCNJ11 mutations suggests that germline mosaicism may be common. The possibility of germline mosaicism should be considered when counseling recurrence risks for the parents of a child with an apparently de novo KCNJ11 activating mutation.     

Service and Education: The Association Between Workload,Patient Complexity,and Teaching on Internal Medicine Inpatient Services

Background

Attending rounds remain the primary venue for formal teaching and learning at academic medical centers. Little is known about the effect of increasing clinical demands on teaching during attending rounds.

Objective

To explore the relationships among teaching time, teaching topics, clinical workload, and patient complexity variables.

Design

Observational study of medicine teaching teams from September 2008 through August 2014. Teams at two large teaching hospitals associated with a single medical school were observed for periods of 2 to 4 weeks.

Participants

Twelve medicine teaching teams consisting of one attending, one second- or third-year resident, two to three interns, and two to three medical students.

Main Measures

The study examined relationships between patient complexity (comorbidities, complications) and clinical workload variables (census, turnover) with educational measures. Teams were clustered based on clinical workload and patient complexity. Educational measures of interest were time spent teaching and number of teaching topics. Data were analyzed both at the daily observation level and across a given patient’s admission.

Key Results

We observed 12 teams, 1994 discussions (approximately 373 h of rounds) of 563 patients over 244 observation days. Teams clustered into three groups: low patient complexity/high clinical workload, average patient complexity/low clinical workload, and high patient complexity/high clinical workload. Modest associations for team, patient complexity, and clinical workload variables were noted with total time spent teaching (9.1% of the variance in time spent teaching during a patient’s admission; F[8,549]?=?6.90, p <?0.001) and number of teaching topics (16% of the variance in the total number of teaching topics during a patient’s admission; F[8,548]?=?14.18, p <?0.001).

Conclusions

Clinical workload and patient complexity characteristics among teams were only modestly associated with total teaching time and teaching topics.