Noninvasive assessment of myocardial involvement in patients with systemic sclerosis: role of signal averaged electrocardiography

OBJECTIVE

To assess the role of late ventricular potentials (LVP) in detecting early myocardial involvement in patients with systemic sclerosis (SSc).

METHODS

Seventy-seven patients with SSc (68 women, 9 men, mean age 50 +/- 13 yrs) and 33 control subjects (18 women, 15 men, mean age 46 +/- 10 yrs) underwent resting electrocardiogram (ECG), 24 h Holter monitoring, complete echocardiographic and Doppler echocardiographic examination, and signal averaged ECG at high pass setting of 40 Hz, with the low pass fixed at 250 Hz. Patients with SSc underwent resting myocardial scintigraphy and radionuclide angioventriculography.

RESULTS

The prevalence of LVP at 40 Hz was 20.5%. Compared to control subjects, patients with SSc showed higher prevalence of septal infarction pattern (p = 0.05), complex ventricular arrhythmias (p = 0.03), pulmonary arterial hypertension (p < 0.001), and LVP (p = 0.02). Forty-four patients with SSc (57.1%) had resting perfusion defects by myocardial scintigraphy. Fourteen of 15 patients with LVP showed perfusion defects compared to 29 of 58 without LVP (p = 0.002). Linear regression analysis showed that myocardial perfusion defect score was significantly correlated to either the filtered QRS duration, or the duration of low amplitude signals < 40 microV of the terminal QRS, or the root mean square voltage of the last 40 ms of the QRS complex. After a mean followup period of 20 months, 8 patients died. In 2 patients who died suddenly, LVP were present.

CONCLUSION

Signal averaged ECG is a sensitive and inexpensive technique in the clinical assessment and followup of patients with SSc.

Cardiac involvement in Behçet's disease

To assess the prevalence and the extent of cardiac involvement in patients with Behçet's disease and to investigate the possible causes that may predispose to this involvement, 30 patients affected by Behçet's disease and 30 normal control subjects were submitted to M-mode, two-dimensional, and Doppler echocardiographic evaluation. Moreover, antinuclear and anticardiolipin autoantibodies were determined in the sera of both patients and control subjects. Finally, HLA-B51 positivity was assessed in the patients and in a historical control group. Mitral valve prolapse was observed in 50% and proximal aorta dilatation in 30% of the patients. There was a significant difference in the rate of these abnormalities in comparison with the control group. Left ventricular function parameters were similar between the two groups. The positivity rate of antinuclear and anticardiolipin autoantibodies was very low (7%), without differences between the groups. HLA-B51 was detected in 82.7% of the patients versus 21.7% in the control group (p < 0.00001). In conclusion, this study demonstrates a high rate of cardiac abnormalities in patients with Behçet's disease.

[Isolated tricuspid valve insufficiency of rheumatic origin]

We present 2 patients with a history of rheumatic fever and isolated tricuspid insufficiency diagnosed by transthoracic Doppler echocardiography. Other factors leading to such a rare organic tricuspid involvement were carefully ruled out.

The antisense bcl-2-IgH transcript is an optimal target for synthetic oligonucleotides

In most human follicular B cell lymphomas the bcl-2 gene is up-regulated as a result of the t(14;18) chromosomal translocation generating a hybrid bcl-2-IgH mRNA. Recently, we have identified in t(14;18)-positive cells a bcl-2-IgH mRNA in the antisense orientation, putatively responsible for the overexpression of bcl-2. Herein we show that this chimeric antisense transcript is an optimal target for synthetic oligodeoxynucleotides (ODNs). A variety of sense-oriented oligonucleotides have been designed that target the antisense transcript in regions endowed with a sequence specificity presumably restricted to an individual cell line (the bcl-2-IgH fusion regions) or extended to all t(14;18) cells (the ectopic bcl-2 segment upstream from the major breakpoint region and the IgH segment). All sense-oriented ODNs complementary to the antisense transcript induced an early strong inhibition of cell growth and a late fulminant cell death. As expected, the activity of ODNs targeting the fusion region was restricted to each individual cell line, whereas the activity of all ODNs targeting the common bcl-2 and IgH segments was extended to all t(14;18) cell lines tested. These sense ODNs were not effective in untranslocated cell lines. Antisense-oriented ODNs, complementary to the bcl-2-IgH mRNA, and control ODNs (scrambled, inverted, or mismatched) were biologically ineffective. The selectivity and efficacy of all sense ODNs tested provide support for the development of therapeutic ODNs targeting the bcl-2-IgH antisense transcript expressed in human follicular lymphomas.

Plasma endothelin-1 levels during transient acute myocardial ischaemia in men: effects of coronary revascularization

The endothelium-derived peptide endothelin-1 (ET-1) was evaluated in 14 male patients [mean age 52.74 years (SEM 1.10)] affected by coronary artery disease during a bicycle electrocardiographic stress test and dipyridamole echocardiogram. Both tests were performed before and after coronary revascularization. Fourteen healthy male subjects served as controls [mean age 53.21 years (SEM 1.63)]. Baseline plasma endothelin-1 levels were higher (P < 0.0001) in ischaemic patients [1.81 pg mL-1 (0.15, n = 14)] than in control subjects [0.61 pg mL-1 (0.03, n = 14)], but did not increase with exercise in both groups. Similar results were obtained with dipyridamole infusion. Endothelin-1 levels significantly decreased after coronary revascularization [before: mean 1.81 pg mL-1 (SEM 0.15, n = 14); after: mean 1.16 pg mL-1 (SEM 0.11), P < 0.002], without changes in the peptide response to both tests. In conclusion, elevated plasma endothelin-1 concentrations were found in patients with stable angina compared with non-ischaemic subjects. No changes were observed during exercise or dipyridamole infusion in both groups. Coronary revascularization was followed by a significant decrease in plasma endothelin-1 levels.

Relationship between cutaneous and pulmonary involvement in systemic sclerosis

OBJECTIVE

Pulmonary disease may shorten survival in patients affected by systemic sclerosis (SSc). However, pulmonary involvement may commonly be silent, whereas skin fibrosis is usually the clinical feature drawing most attention. We investigated the relationship between cutaneous and pulmonary involvement during SSc.

METHODS

We studied 52 patients (mean age 50.2 +/- 13.7 years) affected by SSc (mean duration of disease 13.8 +/- 9.5 years). Twenty-eight had the diffuse form of the disease (dSSc) and 24 the limited form (lSSc). All patients underwent pulmonary function studies, high resolution computed tomography (HRCT) of the lungs, and complete echocardiographic examination. Pulmonary artery systolic pressure was measured by Doppler echocardiography. Pulmonary interstitial fibrosis and skin fibrosis were evaluated using a point system.

RESULTS

Mean percentages of predicted values of forced vital capacity and total lung capacity were significantly reduced in patients with dSSc compared to lSSc (80.0 +/- 18.9 vs 98.4 +/- 16.8%, p < 0.001; and 81.3 +/- 13.9 vs 92.1 +/- 14.2%, p < 0.01, respectively). The overall HRCT score was 6.1 +/- 4.9, with no significant differences between disease subgroups. However, a HRCT score of 10 or more was present in 10 patients with dSSc vs 2 patients with lSSc (p = 0.02). Pulmonary hypertension was present in 27 patients, 15 with lSSC and 12 with dSSc (p = NS). No significant correlation was observed between skin score and lung volumes, carbon monoxide diffusing capacity, HRCT score, or pulmonary artery systolic pressure for all patients and subgroups.

CONCLUSION

Extent and severity of cutaneous and pulmonary involvement in SSc are not directly correlated. Nevertheless, different patterns of pulmonary involvement between SSc subgroups were observed. Restrictive lung disease was more frequent in patients with dSSc, while a trend to higher prevalence of pulmonary hypertension was observed in patients with lSSc.

Relationships between electrocardiographic and echocardiographic findings in systemic sclerosis (scleroderma)

We assessed the prevalence of electrocardiographic abnormalities in patients with systemic sclerosis and evaluated their functional significance through a comparison with echocardiographic findings. Seventy-two patients with systemic sclerosis and 64 controls underwent resting electrocardiogram (ECG) and M-mode, two-dimensional, Doppler and color Doppler echocardiography. Electrocardiographic abnormalities were observed in 48.7% of patients. Conduction disturbances (27.7%) infarction pattern (13.8%), non-specific ST-T wave changes (13.8%) and right ventricular hypertrophy (11.1%) were the most frequent abnormalities. QTc interval was significantly longer in patients with systemic sclerosis than in controls. Significant differences between patients and controls were found in the prevalence of long QTc interval (p = 0.0016) infarction pattern (p = 0.0016), right ventricular hypertrophy (p = 0.007) and non-specific ST-T wave abnormalities (p = 0.0016). All patients with infarction pattern and 90% of patients with prolonged QTc interval had some echocardiographic abnormalities. Electrocardiographic signs of right ventricular hypertrophy were 16% sensitive and 93% specific for pulmonary hypertension; the sensitivity and specificity of the combination of right ventricular hypertrophy, right atrial enlargement and right bundle branch block were 35% and 90%, respectively. Standard ECG is useful to assess cardiac involvement in patients with systemic sclerosis. If infarction pattern, right ventricular hypertrophy or long QTc interval are present, a cardiac involvement is very likely.

Ruptured aortic cusp aneurysm in infective endocarditis

We describe a patient affected by infective endocarditis with aortic aneurysm, waiting for valve replacement, in which aortic cusp rupture determined sudden heart failure. Diagnosis was performed by serial transthoracic echocardiograms and successful surgical valve replacement was performed in emergency.

1,25(OH)2-vitamin D3 stimulation of phospholipases C and D in muscle cells involves extracellular calcium and a pertussis-sensitive G protein

The steroid hormone 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] activates in chick myoblasts the breakdown of phosphoinositides by phospholipase C and the hydrolysis of phosphatidylcholine by phospholipase D. Extracellular Ca2+ requirement and GTP-binding protein mediation of 1,25(OH)2D3-dependent activation of phospholipases C and D were investigated in cells prelabelled with [3H]glycerol or [3H]arachidonic acid. Generation of diacylglycerol by phospholipase C and phosphatidylethanol by phospholipase D were shown to be dependent on extracellular calcium, since both responses were suppressed by EGTA and the Ca(2+)-channel blockers nifedipine and verapamil, and were mimicked by the calcium ionophore A23187. The G-protein activators guanosine 5'-O-(3-thiotriphosphate) and AlF4- strongly enhanced diacylglycerol and phosphatidylethanol release in myoblasts while guanosine 5'-O-(2-thiodiphosphate), which inhibits G-protein-mediated signals, abolished 1,25(OH)2D3-dependent diacylglycerol and phosphatidylethanol release. Bordetella pertussis toxin pretreatment suppressed the hormone action. These results suggest that 1,25(OH)2D3-stimulation of phosphoinositide-specific phospholipase C and phospholipase D in chick myoblasts is mediated by a pertussis-sensitive GTP-binding protein(s) and the influx of extracellular calcium.

A bcl-2/IgH antisense transcript deregulates bcl-2 gene expression in human follicular lymphoma t(14;18) cell lines

The 14;18 chromosome translocation, characteristic of most human follicular B-cell lymphomas, juxtaposes the bcl-2 gene with the IgH locus, creating a bcl-2/IgH hybrid gene. By mechanisms that are still under investigation, this event increases the cellular levels of the bcl-2 mRNA and thereby induces an overproduction of the antiapoptotic BCL-2 protein which is likely responsible for neoplastic transformation. In an effort to identify potential upregulators of bcl-2 activity in t(14;18) cells, we found, by strand-specific RT-PCR, a bcl-2 antisense transcript that is present in the t(14;18) DOHH2 and SU-DHL-4 but not in the t(14;18)-negative Raji and Jurkat lymphoid cell lines, and thus appears to be dependent on the bcl-2/IgH fusion. This antisense transcript is a hybrid bc1-2/IgH RNA, that originates in the IgH locus, encompasses the t(14;18) fusion site and spans at least the complete 3' UTR region of the bcl-2 mRNA. To achieve some insight into its biological function, we treated the t(14;18) DOHH2 cell line with oligonucleotides (ODNs) by specifically targeting the bc1-2/IgH antisense strand. These ODNs lowered bcl-2 gene expression, inhibited neoplastic cell growth by inducing apoptosis. We would like to propose the hypothesis that the bc1-2/IgH antisense transcript may contribute, by an unknown mechanism, to upregulation of bcl-2 gene expression in t(14;18) cells. The possibility has been considered that the hybrid antisense transcript mask AU-rich motifs present in the 3' UTR of the bcl-2 mRNA characterized in other genes as mRNA destabilizing elements.

White-coat hypertension and cardiac organ damage in elderly subjects

PURPOSE

The aim of this study was comparing the cardiac mass in elderly normotensive subjects and elderly white-coat hypertensive patients by examining in perspective, in consecutive patients, office blood pressure (BP), ambulatory BP, and echocardiographically determined left ventricular mass.

PATIENTS AND METHODS

We studied 42 elderly patients attending a hypertension unit: of these, 22 (mean age 68.7 +/- 3.2 years) had persistent > 90 mm Hg office diastolic blood pressure (DBP), > 140 mm Hg systolic blood pressure (SBP) and < 142/90 mm Hg daytime ambulatory BP (white-coat positives); the remaining 20 (mean age 67.4 +/- 2.2 years) had < 90 mm Hg office DBP, < 140 mm Hg SBP and < 142/90 mm Hg daytime ambulatory BP (normotensives). White coat-patients (n = 22) were selected from a series of 75 consecutive newly diagnosed and never treated patients with mild hypertension (casual DBP constantly between 90 mm Hg and 105 mm Hg).

RESULTS

Neither left ventricular mass index (89.9 +/- 23.1 vs 91.8 +/-25.4 P = NS and +/- 25.4 P = NS) and left ventricular mass/height, (115.4 +/- 17.1 vs 119.6 +/- 18.3 P = NS), nor relative wall thickness (0.31 +/- 0.44 vs 0.33 +/- 0.05 P = NS) were significantly higher in white-coat hypertensives as against normotensives. Neither did we find a relevant difference between left atrial diameters in the above considered groups (3.28 +/- 0.41 vs 3.32 +/- 0.37). In fact 81.8% of white-coat hypertensives had left ventricular normal geometry; whilst 13.6% only had concentric remodeling. Age and sex were associated with left ventricular mass index, left ventricular mass/height and relative wall thickness. Multiple regression analysis revealed that it is ambulatory, not office BP that carries independent information about relative wall thickness and left ventricular mass indices.

CONCLUSIONS

Since elderly white-coat hypertensive subjects did not display a greater cardiac involvement than age-matched normotensives, they should be treated as such.

Twenty-four hour heart period variability in systemic sclerosis

OBJECTIVE

In patients with systemic sclerosis (SSc), an autonomic dysfunction has been implicated in the pathogenesis of Raynaud's phenomenon and gastrointestinal symptoms. To evaluate cardiovascular autonomic function we analyzed the heart rate variability (HRV) on 24 h electrocardiogram recordings.

METHODS

In 50 patients diagnosed with SSc and 24 control subjects HRV was analyzed for both frequency and time domain.

RESULTS

Frequency domain analysis showed reduction of low frequency and high frequency values in the patients with SSc compared to controls (5.52 +/- 0.74 vs 6.04 +/- 0.78 In(ms2), p = 0.007; and 4.17 +/- 0.97 vs 4.74 +/- 0.97 In(ms2), p = 0.021, respectively). Analysis in time domain showed no significant differences in any variable between groups. There were no significant differences between the diffuse and the limited form of SSc. Number of ventricular ectopic beats, prevalence of frequent ventricular ectopy, and supraventricular tachycardia episodes were increased in the patients with SSc compared to controls.

CONCLUSION

Spectral analysis of heart period variability suggests cardiovascular autonomic dysfunction in patients with SSc. Better understanding of this complication could help delineate new strategies for the treatment of SSc.

Terminally L-modified oligonucleotides: pairing, stability and biological properties

An oligodeoxynucleotide (ODN), capable of reducing the growth of human B lymphocytes carrying the t(14;18) chromosome translocation, was prepared in different 'chemical versions': unmodified phosphodiester, phosphorothioate and phosphodiester capped with L-2'-deoxycytidine. Their binding affinity to the complementary synthetic target was studied by the melting point assay. The ODNs, administered to DOHH2 cells, were compared for stability in the culture medium, cellular uptake, time course of the intact sequence concentration within the cell and ability to inhibit cell growth. The 5', 3'-L-capped derivative and the phosphorothioate had comparable potency, superior to that of the unmodified ODN, in agreement with the concentration of undegraded ODNs within the cell.

Analysis of antisense oligonucleotides by capillary electrophoresis, gel-slab electrophoresis, and HPLC: a comparison

Three techniques are evaluated for assessing the purity of synthetic oligodeoxyribonucleotides: reversed phase high-performance liquid chromatography (RP-HPLC), polyacrylamide gel-slab electrophoresis (PAGE), and capillary zone electrophoresis highly concentrated (18% T) entangled polymer networks (CZE). RP-HPLC does not seem to be able to discriminate and resolve the spectrum of failed sequences expected to accompany an oligonucleotide of a given length. The purity data, as given by the manufacturer, are most often close to 100%. PAGE in 20% T matrices, followed by ethidium bromide staining, gives a good resolution of failure sequences and purity assessments decidedly more realistic. CZE in 18% liquid polyacrylamide is able to resolve to baseline all shorter fragments and to give a precise evaluation of the amount of impurities, based on the intrinsic DNA absorbance at 254 nm. Most of the 18 mer oligonucleotides (and of their phosphorothioate derivatives) analyzed by us, as supplied by three different manufacturers, were found to be contaminated by a spectrum of failed and truncated sequences, ranging in size from 7 mer to 17 mer. The purity data rarely exceeded 80% and most often were of the order of 60%-70%. Conditions for a good routine performance of the CZE technique are described.

Oligonucleotides induce apoptosis restricted to the t(14;18) DHL-4 cell line

Most human follicular B-cell lymphomas are associated with t(14;18) chromosome translocation that joins the bcl-2 gene with the IgH locus. This hybrid gene causes upregulation of BCL-2 protein expression, endowing cells with survival advantage. Although early BCL-2 overexpression is definitely responsible for immortalization/transformation, its exact role in the overt transformation as well as in the maintenance of the tumor phenotype is not known. The capacity of oligodeoxynucleotides (ODN) to modulate gene expression specifically has been exploited to downregulate the overexpression of BCL-2 protein in the SU-DHL-4 human follicular B-cell lymphoma line by the use of sense ODN or antisense ODN or antisense ODN designed to encompass the unique nucleotide sequence in the fusion region of the hybrid transcript. The specific downregulation of the bcl-2 transcript and of the relevant BCL-2 protein in the treated cells activated programed cell death and inhibited growing cells. The antitumor activity was restricted to the DHL-4 cell line carrying the specific nucleotide sequence at the bcl-2/IgH joining region. Thus, DHL-4 lymphoma cells derived from the acute phase of human follicular B-cell lymphoma, although endowed with additional activated oncogenes, were growth inhibited by bcl-2 downregulation with additional activated oncogenes, were growth inhibited by bcl-2 downregulation in a genetically restricted fashion. The biological activity was exerted exclusively by ODNs synthesized in the sense orientation. The sense ODNs have been proposed to anneal the hybrid bcl-2/IgH antisense RNA as identified in this study.

Quantitation of bcl-2 oncogene in cultured lymphoma/leukemia cell lines and in primary leukemia B-cells by a highly sensitive RT-PCR method

BACKGROUND

The bcl-2 gene, isolated from the t(14;18) chromosomal translocation breakpoint, is able to prevent apoptotic death induced by various stimuli in different tissues. Therefore bcl-2 oncogene expression could be a key parameter for investigating the molecular mechanisms involved in the apoptosis of normal and neoplastic hematopoietic cells.

METHODS

In order to evaluate bcl-2 expression in both follicular B-lymphomas carrying or not carrying the 14;18 translocation and in lymphatic leukemias, we optimized an internal standard-based method of reverse transcriptase-polymerase chain reaction (RT-PCR) for the rapid quantitation of bcl-2 mRNA cellular levels. A simple purification of the reverse transcription products resulted in very high PCR efficiency, so that radioactive labelling of the amplification products was avoided.

RESULTS

bcl-2 mRNA levels proved to be higher in t(14;18) than in t(14;18) negative cell lines, and higher in primary leukemia pre-B cells than in early-B cells. Tested for sensitivity by identifying minimal residual t(14;18) B cells expressing the bcl-2/IgH gene, this RT-PCR method was able to detect bcl-2/IgH mRNA from just one t(14;18) positive cell out of ten million t(14;18) negative cells.

CONCLUSIONS

The RT-PCR method we optimized appears to be suitable for clinical use in both leukemia/lymphoma characterization and in lymphomatous disease follow-up.

Plasma endothelin-1 levels, pulmonary hypertension, and lung fibrosis in patients with systemic sclerosis

PURPOSE

To investigate the behavior of circulating endothelin (ET)-1 concentrations in patients affected by systemic sclerosis, and to elucidate the possible relationships existing in this disease among plasma peptide levels, pulmonary hypertension, and lung fibrosis.

PATIENTS AND METHODS

Circulating ET-1 levels were determined by reverse-phase, high-pressure liquid chromatography followed by sensitive radioimmunoassay in 20 patients affected by systemic sclerosis (18 women and 2 men, mean age 48.1 +/- 13.7 years) with or without pulmonary hypertension as evaluated by Doppler echocardiography, or lung fibrosis as measured by a score method based on lung examination by high-resolution computed tomography (HRCT). A group of 18 normal volunteers served as controls (15 women and 3 men, mean age 45.0 +/- 10.1 years).

RESULTS

Plasma ET-1 levels were significantly higher (P < 0.001) in patients with systemic sclerosis (1.72 +/- 0.28 pg/mL) than in control subjects (0.63 +/- 0.06 pg/mL). Pulmonary artery systolic hypertension was detected in 10 patients (50%) with systemic sclerosis (56.2 +/- 18.0 mm Hg, range 37 to 97) versus none of the control subjects (30.2 +/- 2.2 mm Hg, P < 0.0001). Lung fibrosis was present in 12 patients (60%), with an HRCT overall score of 9.0 +/- 4.6. There were no significant differences in plasma ET-1 levels between patients with pulmonary hypertension (1.58 +/- 0.20 pg/mL) or without it (1.76 +/- 0.39 pg/mL, P = 0.188, not significant [NS]); or between patients with lung fibrosis (1.65 +/- 0.14 pg/mL) or without fibrosis (1.78 +/- 0.37 pg/mL, P = 0.290, NS). In particular, 6 patients had neither pulmonary hypertension nor lung fibrosis. In these patients, plasma ET-1 levels were similar compared with the others (1.85 +/- 0.49 versus 1.66 +/- 0.13, respectively; P = 0.180, NS). No correlations were observed between ET-1 levels and either pulmonary pressure levels or HRCT overall scores.

CONCLUSIONS

The use of a sensitive assay, highly selective for ET-1, showed higher levels of circulating peptide in patients affected by systemic sclerosis than in control subjects. Neither pulmonary hypertension nor lung fibrosis was accompanied by a further rise in plasma ET-1 concentrations.

Plasma endothelin-1 levels in patients with systemic sclerosis: influence of pulmonary or systemic arterial hypertension

OBJECTIVES

To investigate the behaviour of circulating endothelin-1 (ET-1) in patients affected by systemic sclerosis and to elucidate the relationship between systemic and pulmonary plasma peptide and arterial pressure levels.

METHODS

Plasma ET-1 concentrations were determined in 48 patients affected by systemic sclerosis (41 women, seven men; mean age 47.2 (SD 5.5) years) with or without systemic or pulmonary hypertension (or both). A group of 18 normal volunteers served as controls (15 women, three men; mean age 45.0 (10.1) years).

RESULTS

Plasma ET-1 levels were significantly greater in patients affected by systemic sclerosis (1.65 (0.29) pg/ml) than in controls (0.63 (0.19) pg/ml) (p < 0.0001). Pulmonary artery systolic hypertension alone was present in 14 patients with systemic sclerosis (50.5 (8.49) mm Hg, range 37-67 mm Hg), and systemic hypertension alone (160.7 (5.9)/100.6 (3.2) mm Hg) was present in 11 patients. Both conditions were present in 12 patients, while 11 patients had systemic hypertension. There were no significant differences in plasma ET-1 levels between patients with pulmonary hypertension alone (1.62 (0.21) pg/ml) and those with systemic hypertension alone (1.65 (0.43) pg/ml). In particular, patients with normal pulmonary artery and systemic pressures (n = 11) had plasma ET-1 concentrations identical to those found in patients (n = 12) with both pulmonary and systemic hypertension (1.70 (0.15) v 1.64 (0.35) pg/ml, respectively). No correlations were observed between plasma ET-1 and either pulmonary or systemic pressures.

CONCLUSION

Systemic sclerosis is characterised by increased plasma ET-1 levels, but neither pulmonary nor systemic hypertension are accompanied by further increase in plasma peptide levels.

1,25(OH)2-vitamin D-3 stimulates phospholipase A2 activity via a guanine nucleotide-binding protein in chick myoblasts

The steroid hormone 1,25(OH)2-vitamin D-3 [1,25(OH)2D3] stimulated phospholipase A2 (PLA2) activity in embryonic chick myoblasts releasing [3H]arachidonic acid from the sn-2 position of phospholipids. GTP-binding protein mediation of 1,25(OH)2D3-dependent PLA2 activity was investigated in cells prelabeled with [3H]arachidonic acid. AIF4-, a G-protein activator, mimicked 1,25(OH)2D3-stimulated arachidonic acid release from myoblasts in a dose-dependent manner. Consistent with the involvement of a G-protein in the activation of PLA2 by the hormone, guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S), a stable GTP analogue which activates G-protein mediated signals, strongly enhanced arachidonic acid release in myoblasts. Guanosine 5'-O-(2-thiodiphosphate) (GDP beta S), which competitively inhibits G-protein activation by GTP and its analogues, abolished 1,25(OH)2D3-dependent arachidonic acid release. Bordetella pertussis toxin pretreatment significantly suppressed the hormone action whereas cholera toxin had minor effects on 1,25(OH)2D3 action. Hormone-induced activation of PLA2 was mimicked by the Ca2+ ionophore A23187 and blocked by nifedipine, but was unaffected by neomycin, a phospholipase C inhibitor, ruling out the contribution of phosphoinositide metabolism to arachidonic acid release. These results suggest that 1,25(OH)2D3-stimulation of PLA2 activity in embryonic chick myoblasts is mediated by a pertussis toxin-sensitive GTP-binding protein coupled to influx of extracellular calcium.

Clastogenicity of anthraquinones in V79 and in three derived cell lines expressing P450 enzymes

The clastogenicity of seven anthraquinones was investigated in a V79 Chinese hamster cell line expressing only the reductive pathway enzymes and in three derived cell lines transfected and expressing three rat cytochrome P450 (1A1, 1A2, 2B1). The results have shown that chromosomal aberrations are modulated in similar manner both in parental and transfected V79 cell lines, suggesting that the clastogenicity of these compounds is not mediated by cytochrome P450 dependent monooxygenases.

Tricuspid valve steno-insufficiency in systemic lupus erythematosus

We describe a case of isolated tricuspid steno-insufficiency, diagnosed by transthoracic echocardiography, in a 43-year-old woman affected by systemic lupus erythematosus. Other similar cases were never previously reported.