Hormonal effects on cell proliferation in a human erythroleukemia cell line (K562)

We have investigated the hormonal responsiveness of K562 cells using a serum-substituted in vitro clonogenic assay. Dexamethasone inhibited colony formation by the K562 cells, and the inhibitory effect could be reversed by progesterone (10(-6) M). Fluoxymesterone caused a prominent enhancement of K562 colony growth, whereas estriol had no effect. Stimulation by triiodothyronine was maximal at 10(-7) M, and the thyroid effect could be abrogated by the beta 2-adrenergic antagonist butoxamine in equimolar concentrations. Using standard tissue culture conditions, the beta-adrenergic agent isoproterenol, but not the alpha catecholamine phenylephrine, enhanced the proliferation of K562 cells. When K562 cells were grown under hormone-depleted conditions, they developed responsiveness to phenylephrine and were no longer stimulated by isoproterenol. DbcAMP and prostaglandins of the E series also caused K562 colony enhancement. Prostaglandin F2 alpha had no effect on cell proliferation. Insulin was an effective stimulant of colony formation of K562 cells, as were human growth hormone and ovine prolacin. Bovine growth hormone had no effect. Our results are consistent with the identificaiton of K562 as an erythroid line, and they indicate that K562 cells respond to endocrine hormones in a manner analogous to normal erythroid progenitors.     

Activation of the CPP32 protease in apoptosis induced by 1-beta-D- arabinofuranosylcytosine and other DNA-damaging agents

The response of human myeloid leukemia cells to treatment with 1-beta- arabinofuranosylcytosine (ara-C) includes the induction of apoptosis. Ara-C induced apoptosis is associated with proteolytic cleavage of poly(ADP-ribose) polymerase (PARP) and protein kinase C (PKC) delta. However, the signals involved in this response are unknown. The present studies show that ara-C treatment of U-937 cells is associated with induction of a protease activity that cleaves the tetrapeptides Ac-DEVD- pNA and Ac-DMOD-pNA found at the cleavage sites of PARP and PKC delta, respectively. The ara-C-induced protease activity was sensitive to overexpression of the anti-apoptotic protein Bcl-xL and the baculovirus protein p35. By contrast, overexpression of the cowpox virus protein CrmA blocked apoptosis induced by engagement of the Fas receptor but not that induced by ara-C. CrmA overexpression also had no detectable effect on ara-C-induced cleavage of PKC delta. The results further show that ara-C induces activation of the CPP32 protease by a CrmA- insensitive and p35-sensitive mechanism. Similar results were obtained with cisplatinum, etoposide, and camptothecin. These findings indicate that ara-C and other DNA-damaging agents activate a CrmA-insensitive apoptotic pathway involving CPP32 and that these signals differ from those associated with apoptosis induced by the Fas receptor.     

Sequence homology and structural similarity between cytochrome b of mitochondrial complex III and the chloroplast b6-f complex: position of the cytochrome b hemes in the membrane.

The amino acid sequences of cytochrome b of complex III from five different mitochondrial sources (human, bovine, mouse, yeast, and Aspergillus nidulans) and the chloroplast cytochrome b6 from spinach show a high degree of homology. Calculation of the distribution of hydrophobic residues with a "hydropathy" function that is conserved in this family of proteins implies that the membrane-folding pattern of the 42-kilodalton (kDa) mitochondrial cytochromes involves 8-9 membrane-spanning domains. The smaller 23-kDa chloroplast cytochrome appears to fold in five spanning domains that are similar to the first five of the mitochondria. Four highly conserved histidines are considered to be the likely ligands for the two hemes. The positions of the histidines along the spanning segments and in a cross section of the membrane-spanning alpha helices implies that two ligand pairs, His-82-His-197/198 and His-96-His-183, bridge the spanning peptides II and V, and the two hemes reside on opposite sides of the hydrophobic membrane core. In addition, the 17-kDa protein of the chloroplast b6-f complex appears to contain one or more of the functions of the COOH-terminal end of the mitochondrial cytochrome b polypeptide.     

Predictors for splenectomy among patients with primary chronic immune thrombocytopenia: a population-based cohort study from Denmark

We conducted a nationwide cohort study of adult Danish patients with primary chronic immune thrombocytopenia (cITP) to examine selected patient and clinical characteristics as predictors for splenectomy. We analyzed data from the Danish National Patient Registry and patient medical records from 1996 to 2007. Using Cox regression analyses, we calculated incidence rate ratios (IRRs) and associated 95% confidence intervals (CI) for splenectomy. We included 371 adult cITP patients. Of these, 87 patients (23%) underwent a splenectomy during a median of 3.6 years of follow-up. The majority (84%) of cITP patients who underwent splenectomy had splenectomy within the first year after cITP diagnosis. Predictors for splenectomy included age ≤75 years (adjusted 1-year IRR = 6.79 (95% CI, 2.10–21.90)) at least one platelet count ≤30 × 10⁹/L (i.e., high disease activity; adjusted 1-year IRR = 2.67 (95% CI, 1.37–5.22)) during follow-up and year of cITP diagnosis in early period (1996–2001; adjusted 1 year IRR = 2.37 (95% CI, 1.46–3.85)). Presence of chronic comorbidity was associated with lower rates of splenectomy (adjusted 1 year IRR = 0.58 (95% CI, 0.33–1.05)). Our findings suggest that high disease activity and absence of chronic comorbidity may be associated with higher rates of splenectomy, and that contraindications for splenectomy (i.e., patients’ perceived frailty) cause the physicians to use the procedure cautiously.     

Total and regional myocardial blood flow in aortic regurgitation.

Total, phasic, and regional flow were studied in 12 open-chest dogs with aortic regurgitation. An adjustable catheter device was used to produce aortic regurgitation. Four differently labeled 7 to 9μ microspheres were injected into the left atrium during control, mild (5 to 25 per cent), moderate (25 to 50 per cent), and severe (50 to 80 per cent) regurgitation. Aortic regurgitation (AR) and the ratio of diastolic coronary blood flow to systolic coronary blood flow ($\text{DIAS}\text{SYS}$ RATIO) were measured from the electromagnetic flow tracings. The simultaneous left ventricular and aortic pressures were used to calculate $\text{DPTI}\text{SPTI}$ (diastolic pressure time index to systolic time index). Myocardial flow, flow to major subgroups, and endocardial/epicardial ratios were determined from radioisotope analysis of the left ventricle.Mean absolute control values and mean changes of key variables from control were:

3.

	Control	Mild AR	Mod AR	Severe AR
Heart rate (beats/min.)	163.42	?5.00	?4.831	?8.56
$\text{DPTI}\text{SPTI}$	1.18	?0.121	?0.241	?0.561
Dias/Sys ratio	4.23	?0.28	?1.641	?3.311
Myo. flow (ml./100g./min.)	99.90	?5.63	11.18	21.63
Endocardium (ml./100 g./min.)	97.27	?5.28	10.26	7.39
Epicardium (ml./100 g./min.)	100.15	?7.38	7.88	21.58
$\text{ENDO}\text{EPI}$ ratio	0.99	0.01	0.01	?0.11

1

Denotes significant change from control state (P = 0.05).

The phasic coronary blood flow results in this study are similar to those reported in chronic, intact anesthetized dogs; when the degree of aortic regurgitation increased, there was a significant decrease in diastolic coronary blood flow with an increase in systolic coronary blood flow. Not previously reported are the changes in the distribution of myocardial perfusion. Total myocardial flow increased slightly. There were minimal changes in blood flow to the endocardium which resulted in a slight decrease in the $\text{ENDO}\text{EPI}$ ratio and a decrease in the per cent of flow to the endocardium. These results indicate that, although acute aortic regurgitation produces significant changes in phasic coronary flow, there are much smaller effects on total and regional myocardial blood flow.     

Echocardiographic prediction of outcome after cardiac resynchronization therapy: conventional methods and recent developments

Echocardiography plays an important role in patient assessment before cardiac resynchronization therapy (CRT) and can monitor many of its mechanical effects in heart failure patients. Encouraged by the highly variable individual response observed in the major CRT trials, echocardiography-based measurements of mechanical dyssynchrony have been extensively investigated with the aim of improving response prediction and CRT delivery. Despite recent setbacks, these techniques have continued to develop in order to overcome some of their initial flaws and limitations. This review discusses the concepts and rationale of the available echocardiographic techniques, highlighting newer quantification methods and discussing some of the unsolved issues that need to be addressed.     

Uncoordinated expression of fibrinogen compared with thrombospondin and von Willebrand factor in maturing human megakaryocytes

The localization of three known alpha-granule proteins, thrombospondin (TSP), von Willebrand factor (vWF), and fibrinogen (Fg) has been studied in human megakaryocytes (MK) by immunofluorescence and immunoelectron microscopy. For this study, highly purified populations of MK were prepared from human bone marrow either by counterflow centrifugal elutriation or by cell culture from normal subjects and from two patients with megakaryoblastic leukemia. In normal bone marrow immature MK, TSP, and vWF were observed in the Golgi-associated vesicles and in small immature alpha-granules; in mature MK, they were found in the matrix of the mature large alpha-granules. Surprisingly, Fg was detected neither in the Golgi area, nor in the small precursors of alpha-granules; it was only found in the mature alpha-granules but this labeling was generally weaker than in blood platelets. In order to confirm these differences between the expression of Fg and vWF or TSP additional studies were performed on cultured maturing MK: immunofluorescent and ultrastructural immunogold labeling confirmed that vWF appeared early in the maturation while the same immature MK were negative for Fg. In the late maturation stage, the three proteins were detected in the alpha-granules. In order to know whether Fg was lately synthesized or endocytosed from the outside medium, normal MK were grown in the presence of either normal or afibrinogenemic plasma, and normal serum. Fg was detected only in the alpha-granules of MK grown in normal plasma. Similar results were observed with malignant MK, whose maturation was independent of the culture conditions. In conclusion, this study brings immunocytochemical evidence that vWF and TSP are synthesized by immature MK, whereas Fg appears later in the MK alpha-granules and its expression is dependent of the presence of an exogenous Fg source.     

Acromegaly and heart failure: revisions of the growth hormone/insulin-like growth factor axis and its relation to the cardiovascular system

Cardiomyopathy is a major cause of death in overt acromegaly. Recent progress in research has increasingly revealed the molecular mechanisms concerning growth hormone and insulin-like growth factor in the development of heart failure. In this article, we propose mechanisms according to which heart failure occurs, and we aim to extrapolate this knowledge to more general processes involved in heart failure.