Cloning of a human gene involved in cytochrome oxidase assembly by functional complementation of an oxa1- mutation in Saccharomyces cerevisiae.

The yeast nuclear gene OXA1 is essential for cytochrome oxidase assembly, so that a null mutation in the OXA1 gene leads to complete respiratory deficiency. We have cloned by genetic selection a human OXA1 (OXA1Hs) cDNA that complements the respiratory defect of yeast oxa1 mutants. The deduced sequence of the human protein shares 33% identity with the yeast OXA1 protein. The OXA1Hs cDNA corresponds to a single and relatively highly expressed gene. Oxygen consumption measurements and cytochrome absorption spectra show that replacement of the yeast protein with the human homolog leads to the correct assembly of cytochrome oxidase, suggesting that the proteins play essentially the same role in both organisms.     

Similar CD40 ligand expression on EL-4 thymoma cell lines with widely different helper activity for B lymphocytes.

A mutagenized subclone of the murine EL-4 thymoma (clone B5) is approximately 30 times more potent than parental EL-4 cells in stimulating proliferation and Ig secretion of murine or human B cells by direct cell contact in the presence of appropriate cytokines. In this study we found that CD40 ligand (CD40L) expression was constitutive and very similar on EL-4 B5 and parental EL-4 cells according to Northern blot and flow cytometry. Activation with phorbol 12-myristate 13-acetate (PMA) alone, PMA and ionomycin, interleukin-1 (IL-1) or human T-cell supernatant did not lead to significant CD40L up-regulation. A receptor-binding assay with soluble CD40 did not reveal different ligand affinities. However, murine and human soluble CD40-IgFc fusion proteins inhibited human B-cell stimulation by EL-4 B5 cells in the presence of human T-cell supernatant. Inhibition was 96% when soluble CD40 was added on day 0 of culture and progressively decreased when the CD40 was added subsequently. Ig secretion by cytoplasmic Ig-positive cells was no longer inhibited. These findings imply that, although CD40 ligand is necessary for B-cell activation by EL-4B5 cells, additional molecule(s) must be responsible for the increased helper activity of the EL-4 B5 clone.     

Recombinant 25-kDa CD23 and interleukin 1 alpha promote the survival of germinal center B cells: evidence for bifurcation in the development of centrocytes rescued from apoptosis.

Germinal centers contain a proliferating pool of centroblasts which give rise to non-dividing centrocyte. Centrocytes are programmed to die by apoptosis unless they receive a positive signal for rescue. Rescue, in vivo, is likely to be dependent, initially, on interaction with antigen held on follicular dendritic cells (FDC). A subset of FDC located in that part of the germinal center furthest from centroblasts is particularly rich in CD23. Supernatants containing high levels of soluble CD23 were found not only to encourage the survival of germinal center B cells but also to promote their differentiation toward a plasmacytoid morphology; these activities were diminished following removal of CD23 from the supernatants. Recombinant 25-kDa CD23 was initially found to be incapable of providing the signal for germinal center cell development but on the addition of interleukin 1 alpha which, by itself, was inactive, rescue and differentiation of germinal center B cells were now achieved. Apoptosis in germinal center cells could also be prevented by the ligation of surface CD40 with monoclonal antibody: however, rescue via this pathway was not accompanied by plasmacytoid differentiation. These findings provide a functional rationale to the high level expression of CD23 found within a discrete subset of FDC and indicate a bifurcation in the development of germinal center B cells following their rescue from apoptosis.     

Spontaneous and ligand-induced endocytosis of CD23 (Fc epsilon receptor II) from the surface of B lymphocytes generates a 16-kDa intracellular fragment.

It has been reported that the 45-kDa low-affinity Fc epsilon receptor (Fc epsilon RII) on B cells is cleaved spontaneously from the cell surface to release soluble fragments. This study demonstrates an additional fate of the Fc epsilon RII. 125I-labeled CD23+ B cells were cultured for 24 h at 37 degrees C. After lysis, cell extracts were immunoprecipitated with CD23 monoclonal antibodies. Using this methodology, we demonstrated that an increasing amount of the labeled Fc epsilon RII becomes progressively resistant to externally applied trypsin, indicating that a fraction of the cell surface receptors are internalized. In parallel, a labeled 16-kDa material, recognized by CD23 monoclonal antibodies directed to the lectin-like domain of the Fc epsilon-RII appears inside the cells. Chloroquine does not affect internalization of the Fc epsilon RII, but completely abolishes the formation of the intracellular fragment, suggesting that the receptor is processed by proteolytic cleavage in acidic organelle. In addition, the internalization is enhanced in the presence of CD23 monoclonal antibodies. These data demonstrate that Fc epsilon RII can be internalized by ligand-induced endocytosis and subsequently cleaved in an intracellular compartment. These results also support the view that the Fc epsilon RII is involved in antigen focusing and antigen presentation.     

Influence of nutrition and physical activity on muscle in the very elderly

AGE-RELATED LOSS IN MUSCLE MASS: Aging is associated with a progressive decline in muscle mass (sarcopenia). Age-related sarcopenia results in a 50% decrease in muscle fiber area, especially type II fiber area. There are many consequences related to this reduction in muscle mass including decline in muscle strength and function and impaired functional capacity. PROTEIN INTAKE: Sarcopenia also results in a reduction in the body's major protein pool. Adequate dietary protein to replace obligatory nitrogen loss and to support protein turnover is essential for maintaining muscle mass. It is usually suggested that protein requirements in older subjects are above 1 g/kg/d. PHYSICAL EXERCISE: Sedentary lifestyle may contribute to loss of skeletal mass in elderly people. Exercise can help reverse this deficit and may improve the regeneration potential of muscle fibers.     

Significance of serum troponin I elevation in patients with acute aortic dissection of the ascending aorta

OBJECTIVE: This study evaluated the prevalence of increased cardiac troponin I (cTnI) in patients with acute aortic dissection of the ascending aorta (type A). METHODS AND RESULTS: In 119 consecutive patients with type A acute aortic dissection, serum cardiac troponin I was measured along with clinical, haemodynamic, electrocardiographic and echocardiographic variables obtained on admission. Cardiac troponin I was positive in 28 patients (23.5%; mean +/- SD: 6.1 +/- 14.7 ng/ml) and above the myocardial infarction threshold (1.5 ng/ml) in 12 (10%). Catecholamine infusion (17.9% vs. 4.4%; p = 0.03) and higher value of creatinine (35.7% vs. 15.4%; p = 0.03) were more frequent in patients with elevated troponin.Total mortality was 29.7% (n = 35) and surgical mortality was 16.8% (n = 17). An increased troponin was discriminatory with respect to mortality (OR: 4.1 (1.6-9.9); p = 0.002) in univariate analysis. However, this association was lost when other markers of death (age, stroke, ST-segment elevation, tamponade, catecholamine infusion, renal failure) were added in a multivariate model (OR: 2.2 (0.7-7.4); p = 0.19) indicating that the myocardial loss associated with troponin increase is not in itself a factor of mortality. CONCLUSIONS: Cardiac troponin I elevation is frequent in patients with type A aortic dissection. It might reflect a higher haemodynamic stress but does not necessarily reflect a negative prognosis.     

Ventilation/perfusion (V/Q) scanning in contemporary patients with pulmonary embolism: utilization rates and predictors of use in a multinational study

Journal of Thrombosis and Thrombolysis - Ventilation/perfusion (V/Q) imaging and computed tomography pulmonary angiography (CTPA) are common tools for acute pulmonary embolism (PE) diagnosis....     

Acute renal insufficiency after flurbiprofen treatment in a patient treated with angiotensin converting enzyme inhibitor

We report a case of acute renal insufficiency in a 77 year-old patient who took flurbiprofen as antiplatelet therapy. This is an important observation because it illustrates the potential risk of acute renal insufficiency, when using flurbiprofen before invasive medical examination or surgery in patients receiving long-term treatment with angiotensin converting enzyme inhibitors or angiotensin II inhibitors. This risk is probably underestimated in usual clinical practice.