Efficacy and tolerance of interferon-alpha(2b) in the treatment of chronic hepatitis C virus infection in haemodialysis patients. Pre- and post-renal transplantation assessment

BACKGROUND

Hepatitis C virus (HCV) infection represents an important problem for the dialysis population due to its high prevalence and the long-term development of chronic liver disease, particularly following renal transplantation.

METHODS

In order to assess the efficacy and tolerance of interferon (IFN) in the treatment of chronic hepatitis C in haemodialysis (HD) patients and their clinical course following renal transplantation, a multicentre, randomized, open-label study was conducted to compare IFN therapy vs a control group.

RESULTS

Nineteen HCV RNA-positive patients received 3 x 10(6) U of IFN s.c., three times a week (post-HD), and 17 HCV RNA-positive patients were assigned to the control group. Tolerance to IFN therapy was good in nine patients, while treatment was discontinued in the other 10 due to the occurrence of side effects. HCV RNA was negative at the end of treatment in 14 out of 19 patients (74%) receiving IFN and in one patient (5%) in the control group. Six out of the 14 patients who initially responded to IFN therapy had a virological relapse (43%). Eight patients (42%) remained HCV RNA-negative, three of them until the day that renal transplantation (RT) was performed (7, 12 and 27 months, respectively), as did five patients on HD during the follow-up (27+/-5 months). Eight out of the nine patients (89%) who completed therapy were HCV RNA-negative at the end of treatment, and seven of them (78%) remained HCV RNA-negative during the follow-up on dialysis (21+/-8 months). Mean transaminase (ALT) values were significantly decreased following IFN therapy, while no changes were observed during the follow-up period in the control group. Fifteen patients (10 in the treatment group and five in the control group) underwent RT. Three patients in the treatment group were HCV RNA-negative at RT, and one of them had a virological relapse 20 months after RT, while the other two remained HCV RNA-negative at 3 months and 24 months after RT, respectively. In contrast to the control group, transaminase (ALT) remained within normal limits in all patients in the treatment group. Finally, during the post-RT follow-up, the transaminase mean values were significantly lower in treated patients vs patients in the control group (P<0.05).

CONCLUSIONS

It is concluded that the biochemical and virological response to IFN therapy is good in HD patients. In addition, IFN therapy appears to exert a beneficial effect on the course of liver disease following RT, regardless of the virological response. Despite the fact that IFN therapy was discontinued in 10 out of the 19 patients due to the occurrence of side effects, these disappeared following discontinuation of therapy. Therefore, IFN therapy is advisable for HCV-infected dialysis patients who are candidates for RT.

Monitoring toasting intensity of barrels by chromatographic analysis of volatile compounds from toasted oak wood

Toasting changes both the quantity and the quality of the extractable substances in the oak wood of barrels used for the aging of fine wines and spirits. Mastery and repeatability of toasting are vital in the production of quality barrels to be used for the aging of wines and spirits. In this study, we show that it is possible for a given cooperage to differentiate barrel toasting levels by analyzing a certain number of volatile and semivolatile compounds resulting from the thermal degradation of oak. Toasted wood components, which can be extracted by the wines or spirits during the aging process, are normally analyzed after the wood has soaked in standard alcoholic solutions and can be used to control the intensity of the wood toasting. The results of the comparative analysis presented in this work show that headspace analysis with a microextractive method using a stationary polydimethylsiloxane type phase is a promising technique for analyzing toasted oak wood from barrels. It is easier to use than the traditional maceration and extraction method and provides similar information.

Chronic constrictive pericarditis induced by long-term bromocriptine therapy: report of two cases

OBJECTIVE

To report two cases of chronic constrictive pericarditis that appear to be related to the intake of bromocriptine for Parkinson's disease.

CASE SUMMARY

Two white men (aged 63 and 69 y) were treated with bromocriptine for four (40 mg/d) and two years (30 mg/d), respectively, with a cumulative dose intake of 58.4 and 21.9 g, respectively. The patients experienced dyspnea with bilateral lower-limb edema and pleural effusion, suggesting right cardiac dysfunction. Echocardiography, computed tomography, and cardiac catheterization results were compatible with a diagnosis of constrictive pericarditis, so pericardectomy was performed on both patients. The anatomic pathology examination showed a fibrous pericardium; cultures were sterile. In the first case, pleural effusion recurred seven months after the pericarditis; bromocriptine was suspected and treatment was discontinued. In the second case, just prior to the pericardectomy, an episode of mental confusion occurred and prompted the cessation of bromocriptine therapy.

DISCUSSION

To the best of our knowledge, only one case of constrictive pericarditis induced by bromocriptine therapy has previously been described in the literature.

CONCLUSIONS

Our cases call attention to a possible association between bromocriptine use in patients who have Parkinson's disease and constrictive pericarditis.

Reporter cell lines to study the estrogenic effects of xenoestrogens

In order to characterize the estrogenic activity of chemicals, we established complementary in vitro recombinant receptor-reporter gene assays in stably transfected MCF-7 and HeLa cells. MCF-7 cells which express the endogenous estrogen receptor alpha (ER alpha) were stably transfected with only an estrogen-regulated luciferase gene. These cells enable the detection of compounds which bind to ER alpha or interfere with the induction of ER alpha mediated gene expression. Furthermore, HeLa cells, which do not express endogenous ERs, were transfected with an ER alpha or an ER beta construct together with an estrogen-regulated luciferase gene, or a chimeric GAL4-ER alpha receptor and the corresponding luciferase reporter gene. Finally, we tested these four cellular models as tools to check the estrogenic activities of several potential xenoestrogens and to detect estrogenic activity in wastewater sewage treatment effluents. In all of the models, nonylphenol mixture (NPm), 4n-nonylphenol (4nNP), 2,4'-DDE, 4,4'-DDE and wastewater sewage treatment effluent were active, while PCB mixture (Aroclor 1254), PCB 77, atrazine and lindane (gamma hexachlorocyclohexane) were inactive. Dioxin partially activates the estrogen receptor in MCF-7 cells while in HeLa-derived cell lines, it decreased the estrogenic-induced expression of luciferase.

Measurement of relaxation rates of N(H) and H(alpha) backbone protons in proteins with tailored initial conditions

Several methods are presented for the selective determination of spin-lattice and spin-spin relaxation rates of backbone protons in labeled proteins. The relaxation rates of amide protons in (15)N labeled proteins can be measured by using two-way selective cross-polarization (SCP). The measurement of H(alpha) relaxation rates can be achieved by combining this method with homonuclear Hartmann-Hahn transfer using doubly selective irradiation. Various schemes for selective or nonselective inversion of the longitudinal proton magnetization lead to different initial recovery rates. The methods have been applied to lysine K6 in (15)N-labeled human ubiquitin and to leucine L5 in (15)N- and (13)C-labeled octapeptide YG*G*F*LRRI (GFL) in which the marked residues are (15)N- and (13)C-labeled.

A "dysautonomic" head-up tilt test pattern in elderly patients with neurocardiogenic syncope

The characteristics of neurocardiogenic syncope (NCS) in elderly patients remain unclear. We compared the hemodynamic profiles of young and older patients with consecutive and positive head-up tilt tests (HUT). Continuous, noninvasive, and reliable monitoring of arterial pressure (AP) and heart rate (HR) was done throughout 46 consecutive positive HUTs of symptomatic patients. The population (12-82 years old) was divided into two groups: younger patients, Y (n = 25, < or = 65 years), and older patients, O (n = 21). Changes in AP and HR after the first minute of tilting, during the stable orthostatic phase and during syncope were compared. Except for systolic pressure, baseline hemodynamic parameters were similar in Y and O. No difference appeared in the mean time elapsed before syncope (19+/-9 vs 22+/-2 min). Asymptomatic hypotension was observed, only in O, 1 minute after tilting, followed by a progressive fall in the mean AP before syncope (0+/-0.9 vs -1+/-0.7 mmHg/min) without HR increase (0.7+/-1 vs 0+/-0.6 beats/min). This pressure slope was strongly related to age (r = 0.54, P < 0.001). Hemodynamic recording during HUT identifies a dysautonomic pattern in elderly patients with NCS and the abnormal AP/HR responses to orthostasis may be a feature specific to this population. Although the central mechanism of NCS is common to all ages, the age-related characteristics of the trigger event may indicate the need for specific management at different ages.

[Electrocardiographic aspects of the pathology of the bundle of His]

The ECG appearances of His bundle pathology are very variable and endocavitory recordings are often required to confirm the diagnosis which may be suspected by close analysis of the surface ECG. Truncular AVB is a serious condition as the block is infranodal but with a supraventricular and therefore a narrow QRS complex: it may be median with a double His potential or proximal and distal, which are more difficult to diagnose. Hisian extrasystoles are particularly polymorphic, either overtly, suggesting successively atrial and ventricular extrasystoles, or masked with deceptive pseudo-1st or 2nd degree atrioventricular block. More rarely, hisian tachycardias complicating congenital heart disease in children are observed, particularly in the postoperative period.

Infected total hip arthroplasty--the value of intraoperative histology

Intraoperative histology showed a sensitivity of 100% and a specificity of 98%. These results were better than those observed for the other tests evaluated. Our data provide evidence that intraoperative histology is useful tool in the diagnosis of infected total hip arthroplasty.

Molecular dynamics study of kaliotoxin in water

Kaliotoxin (KTX), a potassium channel blocker found in the venom of the scorpion Androctonous Mauretanicus is a 38 residue polypeptide with a well defined structure consisting of a alpha-helix and a three strand antiparallel beta-sheet interconnected by three disulfide bonds. Although the 3D structure has been determined by NMR, there is a number of features, mainly concerning the conformation and flexibility of the side chains, but also the long range order in the peptide and its fluctuations, that may have escaped the experimental study. These questions are now being addressed using molecular dynamics (MD) simulations. Accordingly, the present work reports the analysis of a 430 ps molecular dynamics trajectory of the polypeptide soaked with 4700 TIP3 water molecules inside a 56 A box. MD calculations were performed with periodic boundary conditions. Analysis of the conformational space sampled by each of the residues along the trajectory, suggests a special behavior of Pro17 and Lys19 both located on the helix. Furthermore, analysis of the relative movements of the secondary structure elements indicates that the alpha-helix and beta-sheets fluctuate in a correlated motion, preserving the tertiary structure of the polypeptide along the trajectory. Finally, analysis of the charge distribution was also examined. The direction of the dipole moment, computed from the center of masses appears to be an interesting feature of the structure probably related to the biological function of the molecule.

Correspondence analysis of protein kinase C (PKC) inhibition by bis-basic substituted benzamides

We describe the synthesis of a novel series of bis-basic substituted benzamides and their relative potency in inhibiting rat brain protein kinase alpha (PKC alpha) activity. None of the compounds inhibited enzyme activity via the catalytic domain but several did via the regulatory domain at 1-5 microM concentrations. Inhibition was comparable to that of several di- and triphenylacrylonitriles and triphenylethylenes. According to a multivariate factor (correspondence) analysis of QSAR descriptors, hydrophobicity (log p) and hydration energy were the most discriminant descriptors, much more so than molecular mass, molar refractivity, polarizability, molecular volume and solvent-accessible surface. Inhibitory activity was correlated with high hydrophobicity and low hydration energy. The higher potency of GL9 (N,N'-oxalyl-bis[(o-amino)[2-(diethylamino)ethyl]-benzamide]) that differed from its congener (GL25) by the presence of an oxamide rather than succinamide moiety was tentatively explained by the greater negative charges associated with the carbonyl groups of its oxamide residue. The higher potency of GL22 (N,N'-tere-phthalyl-bis[(o-amino)[2-(diethylamino)ethyl]-benzamide ] in which an aromatic ring is inserted between two benzamide moieties in para, para' rather than ortho, ortho' positions as in GL23 might be due to a planar conformation facilitating membrane insertion. In conclusion, correspondence analysis is a neat way of highlighting similarities and differences in molecular properties (QSAR descriptors and potency). Therapeutic doses of many classes of drug might interfere with the regulatory domain of PKC alpha if, like our test-compounds, they have basic side-chain(s), high hydrophobicity, low hydration energy, a planar conformation and/or a highly charged reactive (oxamide) moiety.

Determination of indomethacin residues in poultry by high-performance liquid chromatography

A HPLC method using a C18 column and UV detection (254 nm) is described for the determination of indomethacin residues in chicken tissues (liver, muscle and fat). Drug extraction from tissue homogenate in phosphate buffer (pH 3.5) was performed with dichloromethane. Mobile phase was acetonitrile-acetic acid (0.5% in water) (50:50). Indomethacin detection limit was 20 ng/g for the studied tissues. After administration of an oral dose of indomethacin (2 mg/kg), only three of the eight poultry studied showed drug tissue levels, in those cases the levels were below 50 ng/g.

Non-invasive assessment of inspiratory muscle performance during exercise in patients with chronic heart failure

AIMS

The aim of this study was to assess inspiratory performance at rest and during exercise in patients with chronic heart failure in comparison with healthy controls using a non-invasive index: the tension-time index of inspiratory muscles (TTMUS).

METHODS

We studied 13 patients with chronic heart failure (57 +/- 7 years) and 10 control subjects (58 +/- 6 years) at rest and during an incremental maximal exercise test. Measurements included breathing pattern (inspiratory time, total time of respiratory cycle, minute ventilation, tidal volume and respiratory frequency), mouth occlusion pressure and mean inspiratory pressure (calculated as follows: 5 x mouth occlusion pressure x inspiratory time). The maximal inspiratory pressure was measured at rest. TTMUS was calculated from the equation: TTMUS = PI/PIMAX x TI/TTOT, where PI/PIMAX is the ratio of mean inspiratory pressure to maximal inspiratory pressure and TI/TTOT is the ratio of mean inspiratory time to total time of the respiratory cycle.

RESULTS

At rest, the results in patients showed non-significantly higher mouth occlusion pressure, lower maximal inspiratory pressure (P < 0.001), and a higher ratio of mean inspiratory pressure to maximal inspiratory pressure (P < 0.01). There was no difference in the breathing pattern. TTMUS was thus significantly higher in the patients with chronic heart failure (P < 0.001). At maximal exercise (77 +/- 16 W for patients with chronic heart failure vs 142 +/- 27 W for controls, P < 0.001), the ratio of mean inspiratory time to total time of respiratory cycle, the mouth occlusion pressure and the ratio of mean inspiratory pressure to maximal inspiratory pressure were not different. TTMUS was thus comparable in the two groups. During exercise, at comparable workloads (20, 40 and 60 W), the patients showed higher mouth occlusion pressure (P < 0.01) and a higher ratio of mean inspiratory pressure to maximal inspiratory pressure (P < 0.001), whereas the ratio of mean inspiratory time to total time of the respiratory cycle was similar. TTMUS was thus higher in the patients at each workload (P < 0.05).

CONCLUSION

This study shows that the determination of TTMUS at rest and during exercise allows the observation of alterations in inspiratory muscle performance as a result of both reduced inspiratory strength, as measured by the maximal inspiratory pressure, and increased ventilatory drive, as reflected by the mouth occlusion pressure in patients with chronic heart failure. The non-invasiveness of this new index is an additional argument for its use in a clinical setting.

Solution conformation of an immunogenic peptide from HRV2: comparison with the conformation found in a complex with a Fab fragment of an anti-HRV2 neutralizing antibody

The conformation of a [15]-peptide (H-VKAETRLNPDLQPTE-NH2) from VP2 of rhinovirus HRV2 complexed with a Fab fragment was previously shown by X-ray crystallographic studies to be similar to the one found in the corresponding region of HRV1A. Antibodies raised against this peptide bind to and neutralize HRV2. In order to identify structural features preserved in solution that may explain the ability of this short peptide to mimic the structure of the protein surface, the peptide has been studied by NMR in aqueous solution as well as under denaturing conditions. The peptide is shown to be a random coil in solution. However, the sequence forming a 3(10)helix in the complex is biased into a helical conformation according to NOE intensity data as well as from urea and pH titrations. This sequence adopts the same conformation in an unrelated protein. NOE data suggest that a beta-turn found in the complex may be sampled in solution. Also, Glu4, interacting with Arg6 in the crystal, has a reduced pKa value in solution. It is concluded that the local structure present in the random coil state of VP2(156-170) contains enough information to direct the production of antibodies that bind to and neutralize HRV2.

A new method for measuring diffusion coefficients by 2D NMR using accordion spectroscopy

Translational diffusion measurements are a useful tool for studying supramolecular complexes and for characterizing the association state of molecules that aggregate at NMR concentrations. Pulsed field gradients can be used to measure diffusion coefficients. Spectral overlap problems in complex mixtures can be alleviated by using 2D spectroscopy but the need to record a complete series of 2D spectra with increasing gradient strength makes these experiments extremely time consuming. Concerted incrementation of the gradient strength and the evolution time provides a new version of accordion spectroscopy that allows the measurement of individual diffusion coefficients in complex mixtures in a single experiment. Copyright 1998 Academic Press.

[Vasovagal syndromes]

Most cases of dizziness or syncope referred to the emergency department or to services of internal medicine are caused by vasovagal syndromes. They comprise relative bradycardia with vasoplegia, the cardiovascular response to a neurological stimulus. It is possible to distinguish vagal or vasovagal syncope which is very common, the very stereotype reflex syncopes, carotid sinus hypersensitivity sometimes associated with sinus node dysfunction and borderline forms such as orthostatic sinus tachycardia and cerebrovascular syncope. The differential diagnosis is vast, from simple hysteria to severe cardiac disease. Tilt testing should be indicated for diagnosis of most cases of syncope with apparently normal hearts. Therapeutic abstention is the rule, providing certain preventive measures are taken, but, should treatment be necessary, cardiac pacing remains an exceptional modality in vasovagal syncope. Strict clinical and physiopathological studies are still required to determine the long-term prognosis and the underlying mechanisms of these syndromes.

Rapid tamoxifen-induced inactivation of an estrogenic response is accompanied by a localized epigenetic modification but not by mutations

In a previous study (Cancer Res 54: 5860-5866, 1994), we observed irreversible inactivation of a chimeric estrogenic response induced by the antiestrogen 4-hydroxytamoxifen. This rapidly occurring effect (t1/2= 7 days) was not a consequence of a cell selection process, nor of a loss of estrogen receptor functionality, but was a direct antiestrogen effect occurring on every cell at the transcriptional level. In the present study, we analyzed the detailed methylation status of the chimeric gene, and investigated the gene for the presence of mutations. The inactivation process was found to be strictly correlated with a modification at a methylation-sensitive restriction site Not I borne by the integrated gene. As the gene promoter contains part of the Herpes simplex virus promoter for thymidine kinase. which is a CpG-rich promoter, we investigated the CpGs located in this part of the promoter by genomic sequencing procedures. None of these CpGs were methylated, suggesting that the inactivation process was not driven by particular modifications of this foreign part of the promoter. Furthermore, no mutations were found in the entire gene promoter of inactivated cells. In conclusion, the present study highlighted a connection between the rapid silencing of an estrogenic response induced by 4-hydroxytamoxifen, and a localized epigenetic modification of the corresponding gene. No genotoxicity of 4-hydroxytamoxifen was observed. Similar epigenetic modifications might also occur for natural genes, and lead to the acquisition of a new cell phenotype.

Sepsis due to group G Streptococcus after a total hip arthroplasty. A case report

A patient with a total hip arthroplasty developed an aggressive infection with group G Streptococcus. Very few similar cases have been reported, but they all resolved with antibiotics or drainage. A Girdlestone resection was necessary in our case because of loosening and extensive bony destruction. The true incidence may be greater than that reported and the prognosis may be worse.

Physicochemical properties of enrofloxacin

The physicochemical properties of enrofloxacin, a fluoroquinolone that inhibits the activity of bacterial DNA gyrase, are described. Its spectral, solubility and related physicochemical characteristics are discussed. The dissociation behaviour of enrofloxacin was examined by UV spectrophotometry at 25 degrees C in a series of buffers ranging from pH 1 to 10. The corresponding macro- and microscopic dissociation constants were calculated. The apparent n-octanol-water partition coefficients were measured from pH 2 to 10.

Steroidal affinity labels of the estrogen receptor. 3. Estradiol 11 beta-n-alkyl derivatives bearing a terminal electrophilic group: antiestrogenic and cytotoxic properties

With the aim of developing a new series of steroidal affinity labels of the estrogen receptor, six electrophilic 11 beta-ethyl (C2), 11 beta-butyl (C4), or 11 beta-decyl (C10) derivatives of estradiol bearing an 11 beta-terminal electrophilic functionality, i.e. bromine (C4), (methylsulfonyl)oxy (C2 and C4), bromoacetamido (C2 and C4), and (p-tolylsulfonyl)oxy (C10), were synthesized. The range of their affinity constants for binding the estrogen receptor was 0.4-37% that of estradiol; the order of increasing affinity (i) relative to the 11 beta-alkyl arm was ethyl < butyl and (ii) relative to the electrophilic functionality was bromoacetamido < bromine < (methylsulfonyl)oxy. Regardless of the conditions used, including prolonged exposure of the receptor to various pH levels (7-9) and temperatures (0-25 degrees C), the extent of receptor affinity labeling by the 11 beta-ethyl and 11 beta-butyl compounds, if any, was under 10%. This was in sharp contrast to results obtained using 11 beta-((tosyloxy)decyl)estradiol which labeled from 60% to 90% of the receptor hormone-binding sites with an EC50 of approximately 10 nM. Estrogenic and antiestrogenic activities of the compounds were determined using the MVLN cell line, which was established from the estrogen-responsive mammary tumor MCF-7 cells by stable transfection of a recombinant estrogen-responsive luciferase gene. The two 11 beta-ethyl compounds were mainly estrogenic, whereas the three 11 beta-butyl and the 11 beta-decyl compounds essentially showed antiestrogenic activity. The fact that the chemical reactivities of 11 beta-ethyl and 11 beta-butyl compounds were not compromised by interaction with the estrogen receptor made the synthesized high-affinity compounds potential cytotoxic agents which might be able to exert either (i) a specific action on estrogen-regulated genes or (ii) a more general action in estrogen-target cells. Therefore the ability of the compounds (1) to irreversibly abolish estrogen-dependent expression of the luciferase gene and (2) to affect the proliferation of MVLN cells were determined. All electrophiles were able to irreversibly suppress expression of the luciferase gene; the antiestrogenic electrophiles were more potent than the estrogenic ones but less efficient than 4-hydroxytamoxifen, a classical and chemically inert triphenylethylene antiestrogen. Only the antiestrogenic electrophiles decreased cell proliferation; however, they were less potent than 4-hydroxytamoxifen. In conclusion, the synthesized electrophilic estradiol 11 beta-ethyl and 11 beta-butyl derivatives (i) were not efficient affinity labels of the estrogen receptor and (ii) did not display significant cytotoxicity in estrogen-sensitive mammary tumor cells. However, since these derivatives displayed high affinity for the estrogen receptor, they could be used to prepare potential cytotoxic agents which might be selective for tumors affecting estrogen-target tissues, by coupling them with a toxic moiety.

Chronic left main coronary artery occlusion: a complication of radiofrequency ablation of idiopathic left ventricular tachycardia

We describe in this report the development of chronic left main coronary artery (LMCA) occlusion in a young patient 2 years after an uncomplicated, successful ablation of idiopathic left ventricular tachycardia. This complication appears to be a late consequence of trauma to the LMCA during the procedure rather than an acute or subacute embolic event.

3D structure of kaliotoxin: is residue 34 a key for channel selectivity?

Kaliotoxin (KTX) is a natural peptide blocker of voltage-dependent K+ channels. The 3D structure of a truncated analogue of KTX (Fernandez et al. (1994) Biochemistry 33, 14256-14263) was determined by NMR spectroscopy and showed significant differences from structures established for other related scorpion toxins. A recent publication with the structure of the complete toxin (Aiyar et al. (1995) Neuron 15, 1169-1181) did not confirm these differences. In this communication we report NMR data for KTX at pH 3.0, 5.5 and 7.2 and the 3D structure obtained from data at pH = 5.5. Complete KTX displays a folding similar to that of other toxins with an alpha-helix and a beta-sheet linked by two disulphide bonds. The pKa of His 34 is anomalously low (4.7-5.2 depending on the buffer) owing to its interaction with two Lys residues (including the essential Lys 27), the charged N-terminus and the side chain of Met 29. Charged residues are placed symmetrically with respect to an axis that approximately coincides with one of the principal components of the moment of inertia of the toxin. His 34, which occupies a well-defined position between two conserved Cys, is located on the centre of a layer of charged groups. Positively and negatively charged residues are found at the same position in related toxins. It is suggested that electrostatic effects modulate the distances between positive charges in flexible side chains, contributing to the fine tuning of the selectivity toward different channel subclasses and that the approximate coincidence between the moment of inertia and the charge axis facilitate the approach of the toxin to the channel. The very low pKa of His 34 implies that it will be completely unprotonated at physiological pH.

[Classification of regular atrial tachycardia]

ECG criteria which for many years formed the basis of the classification of regular atrial tachycardias may now be completed by the results of endocavitary studies (stimulation and mapping). Flutter is a macroreentry phenomenon in the right atrium, anticlockwise in typical, common or classical forms, and more variable in atypical forms: sometimes antidromic and clockwise, sometimes functional more rapid without a gap of excitability, or in other cases, skirting around the sears of atriotomy, especially right-sided. Tachycardias are paroxysmal and often secondary to reentry; more rarely permanent, they are then often due to increased automaticity especially in young patients. The concordance with surface ECG changes is not perfect and the distinction between flutter and tachycardia often depends on the frequency of the tachycardia and the leads studied.

Incidence and risk factors of hepatitis C virus infection in a haemodialysis unit

BACKGROUND

Hepatitis viruses have become one of the main infectious problems in patients on maintenance haemodialysis. The aim of this study was to prospectively investigate the incidence of de novo hepatitis C virus (HCV) infection in a haemodialysis unit and to identify factors currently involved in HCV transmission to haemodialysis patients.

METHODS

One hundred and fourteen anti-HCV negative and HCV-RNA negative patients who started long-term haemodialysis were followed for a mean period of 36 months (range 18-56). Liver tests and anti-HCV were performed at 6-month intervals. Factors that might be implicated in HCV transmission, such as blood transfusions, sexual habits, surgery and other invasive procedures, were recorded. HCV markers were re-examined in transfused blood and the HCV genotype was investigated in seroconverters to anti-HCV and in patients with previous HCV infection who were treated in the vicinity of those who seroconverted.

RESULTS

Eight patients (7%) seroconverted to anti-HCV and seven of them became HCV-RNA positive. HCV markers, including HCV-RNA, were negative in the blood transfused to seroconverters. No differences between seroconverters and non-seroconverters. No differences found in other risk factors not directly related to haemodialysis. The investigation of HCV genotype suggested that HCV transmission was not restricted to patients treated in the vicinity of previously HCV infected patients. Occasional failure to observe strict measures of asepsis was detected in the haemodialysis unit and this was the only factor that might be incriminating.

CONCLUSIONS

HCV acquisition in patients on haemodialysis is currently not related to blood transfusion, and nosocomial transmission within the haemodialysis unit seems to be the main mechanism of HCV infection. Extremely careful observation of preventive measures seems essential to eradicate HCV transmission in haemodialysis units.

Cytotoxicity and antiestrogenicity of a novel series of basic diphenylethylenes

On the premise that it is necessary to develop antiestrogens with a higher cytotoxic component in order to reduce the risks of the development of heterogeneous malignant cell populations in breast cancer, we studied a novel series of basic diphenylethylenes, for the most part devoid of estrogenic activity, with low antiestrogenicity but much enhanced cytotoxicity compared to the reference drug tamoxifen. The main structural features associated with cytotoxicity were E isomery, substituents of five to eight carbons on the ethylene bond, and dibasicity.

The clinical spectrum of remitting seronegative symmetrical synovitis with pitting edema. The Catalán Group for the Study of RS3PE

OBJECTIVE

To describe the clinical and laboratory features and outcome of patients with remitting seronegative symmetrical synovitis with pitting edema (RS3PE).

METHODS

A retrospective multicenter study of patients with RS3PE fulfilling the following criteria: (1) bilateral pitting edema of both hands, (2) sudden onset of polyarthritis, (3) age > 50 years, (4) seronegative for rheumatoid factor (RF).

RESULTS

27 patients with RS3PE were included, mean age 71.7 years (58-92), 18 men (66.6%) and 9 women (33.3%). Relevant history was noted in 2 patients with polymyalgia rheumatica. Main clinical features were polyarthritis and edema of both hands. Polyarthritis involved metacarpophalangeal joints in 22 patients (81.5%), proximal interphalangeal joints in 19 (70.4%), wrists in 15 (55.5%), shoulders in 13 (48%), elbows in 3 (11.1%), knees in 9 (33.3%), and ankles in 7 (25.9%). All patients were RF negative. Antinuclear antibodies were positive at low titer in 8 patients. Erosions were present in one patient. Two patients developed T lymphoma and one myelodysplastic syndrome.

CONCLUSION

RS3PE is a heterogeneous syndrome the clinical history, presence of erosions, and evolution to hematological diseases in our patients suggest that RS3PE may not be a distinct clinical entity.

[Cotrimoxazole plus rifampicin in the treatment of staphylococcal osteoarticular infection]

OBJECTIVE

To evaluate the efficacy and safety of cotrimoxazol plus rifampicin in staphylococcal osteoarticular infection.

METHOD

Open, non-comparative study of adult hospitalized patients with documented staphylococcal bone infection.

RESULTS

From Feb 1989 to Dec 1993 28 episodes of staphylococcal bone infection were treated in 14 men and 13 women; the mean age was 48 +/- 21 years (range, 11-84). They received cotrimoxazol (7 mg/kg/day of trimethoprim) plus rifampicin (600-1200 mg/day), both orally, every 8 to 12 h with a mean duration of treatment of 34.2 +/- 8.2 days (range, 21 to 55 days). This antibiotic regimen was initiated at the same time that appropriate surgery for each specific condition was undertaken. Diagnoses were postsurgical osteomyelitis (10 cases), infected total hip prostheses (4 cases, one with 2 episodes), osteomyelitis secondary to external pin fixation (5 cases), soft tissue infections linked to orthopedic implants (3 cases), two cases of metatarsal osteomyelitis (one diabetic foot and one patient with polineuropathy), and one case each of chronic osteomyelitis of femur, hematogenous lumbar spondylitis and posttraumatic osteomyelitis. Four patients had bacteremia. The duration of the infection, prior to surgery was less than one month in 12 episodes, 1 month to 2 years in 14, and in 2 cases, of 10 and 13 years, respectively. In 23 episodes the causal agent was Staphylococcus aureus and in 5 cases it was coagulase-negative staphylococci. Patients had received previous parenteral therapy with other antimicrobials during 2-40 days (X: 18.6 +/- 10.2 days). All patients but one had resolution of the infection and are currently asymptomatic 6 months to 5 years posttreatment in the 21 evaluable cases (X: 38 +/- 13.1 months). Five patients had adverse effects secondary to the antibiotic combination and in three these were severe enough to discontinue the antimicrobials. In no case of the 11 patients with post-treatment control cultures were staphylococci recovered from the wound.

CONCLUSIONS

The combination of cotrimoxazole plus rifampicin, both given orally, was highly effective in this selected group of patients. This combination should be considered as a useful alternative therapy of staphylococcal bone infection and deserves further study.

Relationship between circadian changes in renal hemodynamics and circadian changes in urinary glycosaminoglycan excretion in normal rats

Circadian changes in renal hemodynamics and urinary glycosaminoglycan (GAG) excretion were studied in normal Sprague-Dawley rats to further investigate rhythms in kidney function. Urinary water, protein, and GAG excretion, as well as glomerular filtration rate (GFR) and renal plasma flow (RPF), were determined every 4h over the 24h cycle in an attempt to characterize any temporal changes. Urinary flow rate and proteinuria peaked during the dark activity period of the animals, consistently at the same hour, whereas the lowest values were detected during the resting phase. GAG are mucopolysaccharides entering the constitution of the glomerular basement membrane (GBM), which is the key component in the process of glomerular filtration. Similarly, the urinary excretion rate of GAG showed a circadian rhythmicity in phase with urinary water and protein excretion, with markedly increased values observed during the nocturnal phase of the animals. Moreover, GFR and RPF were demonstrated to exhibit large circadian variations in phase with renal excretory rhythmicity, showing nighttime values significantly greater compared to daytime ones. Strong correlations were found between GFR and RPF rhythms, as well as between GAG and GFR, and GAG and RPF rhythms, although the latter were not statistically significant. This pattern suggests that the circadian rhythmicity in urinary excretion rate of GAG in physiological conditions could presumably be secondary to the temporal changes in renal hemodynamics. In this respect, knowledge of renal chronobiology helpfully contributes to increase our understanding of renal physiology.

Circadian rhythms in renal function in hypertensive TGR(mRen-2)27 rats and their normotensive controls

Patients with secondary hypertension frequently display abnormal circadian blood pressure profiles, characterized by a failure to decrease blood pressure at night. The transgenic TGR(mRen-2)27 rat strain, developing fulminant hypertension after the mouse salivary Ren-2 renin gene has been integrated into its genome, provides a fundamental model of genetic hypertension. Because of an inverse circadian blood pressure profile and an unchanged rhythmic pattern of heart rate compared with the normotensive Sprague-Dawley (SPR) strain, it was proposed to serve as an animal model of genetic hypertension. It was the aim of the present study to investigate the circadian rhythmicity in renal function of the transgenic rat to determine whether hypertension and disturbed circadian blood pressure profile would affect kidney function. Urinary water, electrolyte, and protein excretion, as well as glomerular filtration rate and renal plasma flow, were determined in unrestrained freely moving transgenic hypertensive (TGR) and SPR normotensive control rats by collecting urine and arterial blood every 4 h. Significant and similar circadian rhythms were found in renal excretion and hemodynamics in both normotensive and hypertensive strains. Peaks occurred in the active dark period, whereas troughs were found in daytime for all parameters. However, it has to be pointed out that, although the circadian profiles were not grossly perturbed in hypertensive animals, some small differences between SPR and TGR strains did exist in renal function. These discrepancies were precisely related to acrophase, showing a slight phase delay, and also to relative amplitude in TGR. This study demonstrates that the inverted circadian blood pressure profile affected only slightly the circadian rhythms in kidney function in TGR compared with SPR. These findings support the notion that time-dependent changes in systemic blood flow may be of greater importance for circadian regulation of kidney function than systemic blood pressure.

Mutation of isoleucine 747 by a threonine alters the ligand responsiveness of the human glucocorticoid receptor

Mutation of isoleucine 747 to threonine in the C-terminal part of the ligand-binding domain (LBD) of the human glucocorticoid receptor (GR) alters the ligand specificity for transactivation. Natural glucocorticoids such as cortisol or corticosterone were completely inactive with the mutant 1747T, whereas synthetic steroids like dexamethasone efficiently stimulated GR 1747T-mediated transactivation. However, the corresponding ligand dose-response curve for dexamethasone-induced transactivation was shifted to higher concentrations when compared with that obtained with the wild type GR. Neither this shift nor the inability of cortisol to activate the 1747T mutant was due to an altered in vitro ligand-binding affinity. In the canonical three-dimensional structure of nuclear receptor LBDs, isoleucine 747 is in the direct vicinity of residues that contribute to the ligand-binding pocket. Moreover, it is located in the C-terminal LBD region, which harbors the conserved core of the activation function AF-2 and undergoes a ligand-induce transconformation, required to generate the surface interacting with putative transcriptional intermediary factors/coactivators of AF-2. The phenotype of 1747T mutant is discussed in view of the possible consequences of the mutation on the various events which, according to the model, lead to a transcriptionally competent AF-2.

[Chronotoxicology, a relatively unknown approach in toxicology]

Biorhythmicity of living organisms is well-known for many decades by numerous studies in cell biology, in physiology and more recently in pharmacology. Reality of temporal changes in structures and functions of biological systems is clear whatever their complexity level. Such temporal variations can explain that the same xenobiotics, whatever its origin (pathogenous, medicamentous or toxic) does not induce the same efficacity or side effects in a living organisms, if it is given at different hours in the day or at different seasons in the year. This review considers the classical and recent data of the temporal dimension of the toxicology, so called chronotoxicology, describing as well experimental aspects as clinical ones showing the influence of time administration of drugs largely used in clinic with a poor unfair therapeutic index on their efficacity, tolerance and toxicity. Toxicological studies using lethal or sublethal doses with specific organ targets as liver, ear, digestive tractus or kidney will be described. Conclusions of this review evidence the necessity to precise for such chronotoxicological experiments the time of the day and the month of the year where they are performed.

[Circadian changes in physiological urinary excretion of glycosaminoglycans in healthy rats]

Particular chemical structure and original molecular arrangement make the glomerular basement membrane (GBM) to play a key role in the glomerular filtration, by restraining selectively the transglomerular pathway of high molecular weight charged macromolecules. The present study gives evidence, for the first time in the literature, of circadian changes in physiological urinary glycosaminoglycans (GAGs) excretion, main components of the GBM, in normal rats. Urine was collected every 4 hours during 6 consecutive spans in 45 Sprague-Dawley rats, housed in individual metabolism cages (8.00-12.00, 12.00-16.00, 16.00-20.00, 20.00-00.00, 00.00-04.00 and 04.00-08.00). GAGs, water, protein and electrolyte excretion were quantified in each sample. The analysis of these solute temporal changes was done by the cosinor method and shows that a circadian rhythm can be detected. These rhythms exhibit a significant increase between 20.00 and 8.00, with a peak between 00.00 and 04.00 and a minimum between 12.00 and 20.00. A precise estimation of the rhythmic characteristics permitted to detect the acrophase of each parameter nearly at the same time, respectively at 23.25 for diuresis, 23.33 for GAGs, 23.32 for proteins, 23.32 for sodium and 23.44 for potassium excretion. Such chronophysiological data suggest a tight correlation between urinary GAGs excretion and urinary water and electrolyte excretion in physiological conditions, in normal rats. Because of the great complexicity of the factors involved in the kidney the renal excretion regulation, the different origins of these temporal changes are largely discussed.

[New indications for cardiac pacing]

New indications have recently appeared for cardiac pacing with haemodynamic and antiarrhythmic objectives without any symptomatic bradycardia. The best documented indication, though relatively rare, is stimulation of obstructive hypertrophic cardiomyopathy; initially reserved for cases with favorable results of an acute haemodynamic test, it is now used in other cases without this criterion; hypertrophic cardiomyopathy without permanent obstruction, atrial fibrillation or left bundle branch block. The improvement observed during follow-up is always greater as a real remodeling of the myocardium seems to occur with ventricular dilatation and/or septal thinning. However, the position of the atrial, and above all, of the ventricular pacing catheters is critical as is regulation of the pacemaker which should allow complete ventricular capture with an AV delay allowing good filling. The follow-up of these patients must therefore be regular and the effects on longevity are unknown. DDD pacing has also been proposed in dilated cardiomyopathy. The results are contradictory and only very selected cases with left bundle branch block and long PR interval seem justified with, again, optimisation of the pacing sites with high septal or biventricular stimulation. Recurrent atrial tachycardia, special algorithms preventing extrasystoles have been tried with variable results. In cases with inter-atrial block, atrial resynchronisation by bi-atrial stimulation has been assessed with promising results but many technical problems remain unsolved.

An atypical French form of pyruvate carboxylase deficiency

A further case of pyruvate carboxylase deficiency, French type, with a particular clinical presentation and evolution is described. The initial neonatal symptoms started with respiratory distress, severe metabolic acidosis and a tendency to hypoglycemia. However, the clinical course was not rapidly deteriorating. At the age of 6 months he presented acute neurological symptoms, respiratory difficulty, lactic acidosis and hyperammonemia. Amino and organic acid abnormalities strongly suggested pyruvate carboxylase deficiency, which was confirmed by enzymatic studies in cultured fibroblasts and liver necropsy. Progressive deterioration and bronchopneumonia with cardiac failure and renal insufficiency led to death. Anatomic-pathologic studies revealed periventricular cysts and diffuse hypomyelination. Prenatal diagnosis of a further sibling was performed. The neonatal clinical presentation, biochemical abnormalities, and the presence of periventricular cysts suggested a French phenotype. However, the clinical course was less severe, suggesting a residual enzymatic activity and a possible milder mutation.

Pulmonary oedema in healthy persons during scuba-diving and swimming

The prevalence of pulmonary oedema during scuba-diving is unknown. In our referral centre for diving accidents we have observed several episodes of pulmonary oedema in four previously healthy persons while scuba-diving or swimming. Four events were documented by physical findings, typical chest radiographic changes, and arterial hypoxaemia. Four additional episodes were identified in one of the individuals by a suggestive history. No technical problems with the diving equipment were detectable and none of the individuals reported aspiration of water. In order to gather information about the incidence of pulmonary oedema, we carried out a survey among 1,250 divers. To elucidate possible underlying mechanisms of this complication we investigated forearm vascular resistance, levels of vasoreactive hormones, and left ventricular function by Doppler echocardiography, at room temperature and during cold exposure, in four patients and in healthy control subjects. We found only one additional person with a history suggestive of pulmonary oedema among 460 responders to the survey. We found no differences in forearm vascular resistance, left ventricular systolic and diastolic function, and plasma levels of epinephrine, norepinephrine, cortisol, aldosterone, renin and atrial natriuretic peptide between the patients with a history of pulmonary oedema and the control subjects. We conclude that the occurrence of pulmonary oedema during scuba-diving or swimming is an extremely rare event in healthy individuals. The mechanisms responsible remain unclear.

Pulmonary oedema in healthy persons during scuba-diving and swimming

The prevalence of pulmonary oedema during scuba-diving is unknown. In our referral centre for diving accidents we have observed several episodes of pulmonary oedema in four previously healthy persons while scuba-diving or swimming. Four events were documented by physical findings, typical chest radiographic changes, and arterial hypoxaemia. Four additional episodes were identified in one of the individuals by a suggestive history. No technical problems with the diving equipment were detectable and none of the individuals reported aspiration of water. In order to gather information about the incidence of pulmonary oedema, we carried out a survey among 1,250 divers. To elucidate possible underlying mechanisms of this complication we investigated forearm vascular resistance, levels of vasoreactive hormones, and left ventricular function by Doppler echocardiography, at room temperature and during cold exposure, in four patients and in healthy control subjects. We found only one additional person with a history suggestive of pulmonary oedema among 460 responders to the survey. We found no differences in forearm vascular resistance, left ventricular systolic and diastolic function, and plasma levels of epinephrine, norepinephrine, cortisol, aldosterone, renin and atrial natriuretic peptide between the patients with a history of pulmonary oedema and the control subjects. We conclude that the occurrence of pulmonary oedema during scuba-diving or swimming is an extremely rare event in healthy individuals. The mechanisms responsible remain unclear.

RAR-specific agonist/antagonists which dissociate transactivation and AP1 transrepression inhibit anchorage-independent cell proliferation

Using retinoic acid receptor (RAR) reporter cells specific for either RAR alpha, beta or gamma, we have identified synthetic retinoids which specifically induce transactivation by RAR beta, while antagonizing RA-induced transactivation by RAR alpha and RAR gamma. Like RA, these synthetic retinoids allow all three RAR types to repress AP1 (c-Jun/c-Fos) activity, demonstrating that the transactivation and transrepression functions of RARs can be dissociated by properly designed ligands. Using AP1 reporter cells, we also show that glucocorticoids or vitamin D3, together with either RA or these 'dissociating' synthetic retinoids, can synergistically repress phorbol ester-induced AP1 activity. RA, but not these 'dissociating' retinoids, induced transcription of an interleukin-6 promoter-based reporter gene transiently transfected into HeLa cells together with RARs. Using Ki-ras-transformed 3T3 cells as a model system, we show that both RA and the 'dissociating' retinoids inhibit anchorage-independent cell proliferation, suggesting that retinoid-induced growth inhibition may be related to AP1 transrepression.

Prolonged treatment of breast cancer cells with antiestrogens increases the activating protein-1-mediated response: involvement of the estrogen receptor

At micromolar (pharmacological) concentrations, the action of tamoxifen on the proliferation of estrogen-dependent cells can be mediated not only by the estrogen receptor (ER), but also by other target molecules, such as protein kinase-C (PKC), which are easily inhibited by antiestrogens in cell-free experiments. By developing MTLN and MDT cell lines, in which any modulation of PKC activity is reflected by a variation of the expression of an activating protein-1 (AP-1)-controlled firefly luciferase gene, we investigated whether such antiestrogen inhibitory effects on PKC occurred in intact breast cancer cells. Firstly, in short term (4-h) treatment of both cell lines, antiestrogens only inhibited the 12-O-tetradecanoyl-phorbol-13-acetate-induced luciferase activity at very high concentrations (30 microM). A cytolytic effect was also observed. Secondly, in prolonged (4-day) treatments of MTLN (ER-positive) cells, low antiestrogen concentrations (nanomolar) decreased the basal AP-1 response by about 2 and increased the 12-O-tetradecanoyl-phorbol-13-acetate-stimulated AP-1 response by about 3-4. This stimulation was mediated by ER, because 1) dose-response curves established with tamoxifen and hydroxytamoxifen were in agreement with their affinity for ER; 2) when present with antiestrogens, estradiol abolished this phenomenon; and 3) this effect was not observed in MDT (ER-negative) cells. Such a latent activation of AP-1 pathway could appear in the course of breast cancer antiestrogen treatment, in conditions where natural PKC activators are abnormally produced with unexpected consequences on the results of a long term antiestrogen treatment.

[Ventricular fibrillation and defibrillation; electrophysiological bases and clinical applications]

During sinus rhythm, the successive responses to the application of electrical stimuli of increasing intensity during the vulnerable period are cardiac stimulations followed by repetitive ventricular responses and then ventricular fibrillation. An impulse of even greater intensity is not followed by ventricular fibrillation (shock at the upper limit of vulnerability) suggesting that defibrillatory shock is effective only when it does not reinduce fibrillation. Two other hypotheses are also proposed in fibrillation, that of critical mass and that of extension of the refractory periods, in particular after biphasic shocks. Clinically, the measurement of the threshold of defibrillation is difficult as it is a random process which does not obey the all or nothing principle. Ideally, a graph of efficacy versus energy should be constructed but this is only possible under experimental conditions. The effects of different antiarrhythmic drugs have been studied in this manner; in general, the sodium channel blockers improve the energies of defibrillation.

Role of the A/B region of the human mineralocorticoid receptor in aldosterone response selectivity

In transfection experiments performed with wild-type MR, the maximal transcriptional activation of a mineralocorticoid response induced by glucocorticoid was generally similar to that of aldosterone, the natural mineralocorticoid hormone. However, compared to aldosterone, glucocorticoid activity decreased when the A/B region of MR was absent. We describe in this study the synthesis and biological activities of seven mutated MRs differently truncated in the N-terminal region. Using transient expression conditions in MCF-7 cells, the N-terminal domain of MR has been shown to contain a region (residues 254-390) whose deletion led to an apparent "aldosterone selectivity". These results suggest that this region could help to maintain the most transcriptionally active conformation of MR even in the presence of ligands which are not by themselves able to fully induce such a conformation.

[Hip prosthesis infection: diagnostic approach and treatment of 27 cases]

BACKGROUND

Preoperative diagnosis of hip prosthesis infection (HPI) is difficult. There is no therapeutic option which is completely effective and without risk. The aim of this study was to evaluate a diagnostic approach and therapeutic strategy in a group of patients with HPI.

PATIENTS AND METHODS

A retrospective study of 27 episodes of HPI diagnosed by anatomopathologic and/or microbiologic examination of surgical samples was performed.

RESULTS

Twenty-three patients with 27 episodes of HPI out of a total of 24 hip prosthesis (HP) were treated. The infection was early in 15 episodes. The etiologic agents were plasmocoagulase negative staphylococcus (NSP) in 11 cases, P. aeruginosa in 8, S. aureus in 5, Enterococcus sp. in 2 and miscellaneous in the remaining cases. In 2 cases the infection was polymycrobial. Following a mean follow period of 22.6 +/- 15.2 months, 13 out of the 14 patients in whom the prosthesis was withdrawn were cured (in 4 a second prosthesis was implanted), one out of 6 in those in whom the prosthesis remained in situ following debridement, and 2 out of 3 episodes in whom reimplantation was performed over time. The withdrawal of the prosthesis was significantly greater than debridement in the treatment of early infection (p < 0.001). The total mean length of postoperative antibiotherapy was 48.2 +/- 17 days. No differences were observed in the oral versus parenteral treatment (p = 0.22), and nor was prognosis worse in those treated for less than 42 days.

CONCLUSIONS

The authors' experience suggests that attempts to save a hip prosthesis in early infection usually fail. In addition to prosthesis withdrawal or implantation of another prosthesis, six weeks of postoperative antibiotic therapy, which may be oral route, appear to be sufficient.

Kaliotoxin (1-37) shows structural differences with related potassium channel blockers

The three-dimensional structure of kaliotoxin (1-37), KTX(1-37), a toxin from the scorpion Androctonus mauretanicus mauretanicus that blocks calcium-dependent potassium channels, has been determined by NMR. This toxin is homologous with other scorpion toxins such as charybdotoxin (ChTX) or iberiotoxin (IbTX) for which the structures are already known, but the presence of prolines in the expected alpha-helical region suggested that there may be some major difference in the structure of KTX that could be related to its different selectivity. Proline residues are also found in the homologous region of other scorpion toxins such as noxiustoxin or margatoxin. Our results indicate that KTX(1-37) contains the same sequence of secondary structure elements as ChTX but that the helical region is shorter and distorted due to the presence of two prolines. The distortion consists of a bending in the alpha-helix and in the presence of a 3(10) helix turn in the last three residues. Furthermore, the increased length of the extended structure preceding the helix favors a different packing of this part of the molecule with respect to the secondary structure elements. This change in folding modifies the accessibility of the conserved 27Lys which is known, from mutation studies, to be involved in channel blocking by ChTX.

Hydroxytamoxifen induces a rapid and irreversible inactivation of an estrogenic response in an MCF-7-derived cell line

The MVLN cell line was established in our laboratory from MCF-7 cells by stable transfection with the luciferase gene under the control of an estrogen-responsive element from the Xenopus vitellogenin A2 gene. This cell line allowed us to visualize the induction by hydroxytamoxifen of a heterogeneity in the cell population with regard to the expression of the luciferase gene. Treated cells lost their estradiol-inducible luciferase activity, progressively and irreversibly; the luciferase expression of 80% of the cells was irreversibly inactivated by a 12-day hydroxytamoxifen treatment. We showed that this inactivation process was specific for an estrogenic response and was mediated by the estrogen receptor. Tamoxifen itself gave rise to such an inactivation, whereas other compounds belonging to the triphenylethylenic family but differently substituted on the ethylenic carbon and the ICI 164,384 compound were not as efficient. This irreversible inactivation was accompanied by a sharp decrease in the luciferase mRNA level; however, the estrogen receptor function and the cellular transcriptional machinery were not affected by the treatment. Although this antiestrogen treatment neither affected the estrogen-dependent cell growth nor irreversibly inhibited the expression of the natural pS2 gene, these results highly suggest that long-term antiestrogen therapy may lead to some heterogeneity in tumor cells throughout the course of patient treatment.