Pulmonary Haemodynamics in Sickle Cell Disease Are Driven Predominantly by a High-Output State Rather Than Elevated Pulmonary Vascular Resistance: A Prospective 3-Dimensional Echocardiography/Doppler Study

Aims

Patients with sickle cell disease have significant morbidity and mortality. Pulmonary hypertension is suggested to be an important contributor but its nature and severity in these patients and how best to non-invasively assess it are controversial. We hypothesised that a high-output state rather than primary pulmonary vascular pathology may be the major abnormality in sickle cell disease. This study aimed to evaluate the characteristics and severity of pulmonary hypertension in patients with sickle cell disease using detailed echocardiography.

Methods and Results

We undertook a prospective study in 122 consecutive stable outpatients with sickle cell disease and 30 age, gender and ethnicity-matched healthy controls. Echocardiographic evaluation included 3D ventricular volumes, sphericity, tissue Doppler, and non-invasive estimation of pulmonary vascular resistance. 36% of patients had a tricuspid regurgitant velocity ≥2.5 m.s^-1 but only 2% had elevated pulmonary vascular resistance and the prevalence of right ventricular dysfunction was very low. Patients with raised tricuspid regurgitant velocity had significantly elevated biventricular volumes and globular left ventricular remodelling, related primarily to anaemia. In a subgroup of patients who underwent cardiac catheterization, invasive pulmonary haemodynamics confirmed the echocardiographic findings.

Conclusions

Elevated cardiac output and left ventricular volume overload secondary to chronic anaemia may be the dominant factor responsible for abnormal cardiopulmonary haemodynamics in patients with sickle cell disease. 3D echocardiography with non-invasive estimation of pulmonary vascular resistance represents a valuable approach for initial evaluation of cardiopulmonary haemodynamics in sickle cell disease.     

The wages of CIN

Aneuploidy and chromosome instability (CIN) are hallmarks of the majority of solid tumors, but the relationship between them is not well understood. In this issue, Thompson and Compton (Thompson, S.L., and D.A. Compton. 2008. Examining the link between chromosomal instability and aneuploidy in human cells. J. Cell. Biol. 180:665-672) investigate the mechanism of CIN in cancer cells and find that CIN arises primarily from defective kinetochore-spindle attachments that evade detection by the spindle checkpoint and persist into anaphase. They also explore the consequences of artificially elevating chromosome missegregation in otherwise karyotypically normal cells. Their finding that induced aneuploidy is rapidly selected against suggests that the persistence of aneuploid cells in tumors requires not only chromosome missegregation but also additional, as yet poorly defined events.     

Effect of biotin on alkaloid production during submerged cultivation of Claviceps sp. strain SD-58

Addition of biotin to culture medium NL-406 significantly increased alkaloid yield during submerged cultivation of Claviceps sp. strain SD-58. Alkaloid yield was further enhanced by incorporating leucine in biotin-supplemented culture medium. Increased alkaloid production was associated with an increase in the lipid content of cells and in the number of chlamydospores. Biotin deficiency caused a reduction in alkaloid yield and a parallel decrease in lipid content and chlamydospore numbers.     

Assessing the wellbeing of cytoscreeners: experience in two NHS cytology laboratories

OBJECTIVE: Cervical screening programmes in England are in transition as the liquid-based cytology (LBC) method replaces conventional Papanicolaou screening and staff in NHS laboratories are trained to analyse LBC smears. Cytoscreeners and biomedical scientists undertake routine microscopy of slides, but the scientists usually have a wider professional role. Attitudinal surveys were carried out in laboratories where LBC was partially introduced. METHODS: Staff in two cytology laboratories in Greater Manchester were surveyed twice over 6 months. The questionnaire assessed work pressures using scales from the Measures of Work Characteristics instrument, work-related stress using the General Survey version of the Maslach Burnout Inventory, job intentions and job satisfaction. RESULTS: Cytoscreeners, many aged over 50 years, formed over 60% of respondents in both surveys (27/42 in the first survey), and biomedical scientists and doctors, 30%. Both groups were under moderate pressure from work demands in each survey, but cytoscreeners had significantly less autonomy over their working methods (P < 0.001). Although both groups experienced similar levels of exhaustion, cytoscreeners were much more cynical or indifferent towards work in the second survey (P = 0.008) and had lower expectations of being effective (P < 0.001). For the cytoscreeners, there were strong negative correlations in both surveys between cynicism and the work characteristics of influencing decisions and autonomy/control. CONCLUSIONS: The strength of the relationship between work performance and wellbeing serves to emphasize the importance of the new LBC technology in ameliorating low morale where it exists. Further attitudinal research involving larger samples of laboratories is warranted to assess the full impact of this innovation.     

Induction of olfactory mucosal and liver metabolism of lidocaine by 2,3,7,8-tetrachlorodibenzo-p-dioxin

Formulation of drugs for administration via the nasal cavity is becoming increasingly common. It is of potential clinical relevance to determine whether intranasal drug administration itself, or exposure to other xenobiotics, can modulate the levels and/or activity of nasal mucosal metabolic enzymes, thereby affecting the metabolism and disposition of the drug. In these studies, we examined changes in several of the major metabolic enzymes in nasal epithelial tissues upon exposure to the environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), as well as the impact of these changes on the metabolism of a model intranasally administered drug, lidocaine. Results of these studies show that TCDD can induce multiple metabolic enzymes in the olfactory mucosa and that the pattern of induction in the olfactory mucosa does not necessarily parallel that which occurs in the liver. Further, increases in enzyme levels noted by Western blot analysis were associated with increased activities of several nasal mucosal enzymes as well as with enhanced conversion of lidocaine to its major metabolite, monoethyl glycine xylidide (MEGX). These results demonstrate that environmental exposures can influence the levels and activity of nasal mucosal enzymes and impact the pharmacology of drugs administered via the nasal route.     

The catalytic activity of the CD45 membrane-proximal phosphatase domain is required for TCR signaling and regulation.

Cell surface expression of CD45, a receptor-like protein tyrosine phosphatase (PTPase), is required for T cell antigen receptor (TCR)-mediated signal transduction. Like the majority of transmembrane PTPases, CD45 contains two cytoplasmic phosphatase domains, whose relative in vivo function is not known. Site-directed mutagenesis of the individual catalytic residues of the two CD45 phosphatase domains indicates that the catalytic activity of the membrane-proximal domain is both necessary and sufficient for restoration of TCR signal transduction in a CD45-deficient cell. The putative catalytic activity of the distal phosphatase domain is not required for proximal TCR-mediated signaling events. Moreover, in the context of a chimeric PTPase receptor, the putative catalytic activity of the distal phosphatase domain is not required for ligand-induced negative regulation of PTPase function. We also demonstrate that the phosphorylation of the C-terminal tyrosine of Lck, a site of negative regulation, is reduced only when CD45 mutants with demonstrable in vitro phosphatase activity are introduced into the CD45-deficient cells. These results demonstrate that the phosphatase activity of CD45 is critical for TCR signaling, and for regulating the levels of C-terminal phosphorylated Lck molecules.     

Cyclic AMP metabolism and lipolysis in cultured human adipocyte precursors

Triacylglycerol breakdown (lipolysis) results from a series of reactions culminated by activation of "hormone-stimulated" triacylglycerol lipase, an enzyme unique to adipose tissue. We have studied various components of the lipolytic process in human omental adipocyte precursors differentiating in culture. The levels of cyclic AMP, the "second messenger" of lipolytic hormones, were about sixfold higher in fat cell precursors than those in abdominal skin fibroblasts. L-Isoproterenol resulted in significant elevation of cyclic AMP levels in both cell types. Preincubation of intact adipocyte precursors with insulin resulted in significant enhancement of "low Km" cyclic AMP phosphodiesterase activity; in contrast, this hormone had no effect on fibroblast phosphodiesterase activity, a distinctive biochemical difference despite the morphological similarities between the two cell types during the early stages of adipocyte precursor maturation. Incubation of adipocyte precursors with isoproterenol resulted in the release of fatty acids into the medium, findings indicative of "hormone-stimulated" lipase activity and, hence, the operation of the entire "lipolytic cascade"; isoproterenol-stimulated lipolysis was inhibited by insulin. Release of fatty acids from fibroblasts was not observed. Thus, "hormone-stimulated" lipolysis and insulin stimulation of cyclic AMP phosphodiesterase activity are expressed during early stages of human adipocyte precursor differentiation.