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Biomedical subjects

J Caron

Publications and source records attributed to J Caron.

At least 73 records · Page 4Linked to original sources
PubMed1991

[Prognostic value and development of late potentials after aortocoronary bypass. A prospective study of 100 patients].

Ventricular late potentials are post-infarction markers of the risk of ventricular tachycardia and sudden death. In order to assess their prognostic value and evolution after coronary bypass surgery, 100 patients underwent signal-averaged electrocardiographic recordings 24 hours before and 9 days after surgery, and were then prospectively followed up for 40 +/- 8 months. Patients who displayed late ventricular potentials underwent an additional recording at 5 months with 24 hour Holter monitoring. The average age of the patients was 57.0 +/- 8.4 years; 55 had previous myocardial infarction; 32 had triple vessel disease; the mean left ventricular ejection fraction was 59.7 +/- 12.4%. Ventricular late potentials were recorded in 17 patients before surgery and their left ventricular ejection fraction was significantly lower (51.4 +/- 11.5% vs 61.4 +/- 11.9%: p less than 0.05). There was one operative death in a patient with late ventricular potentials. After surgery, late ventricular potentials were only recorded in 6 patients: at the 9th postoperative day in 3 cases and at the 5th postoperative day in 3 cases. Ventricular late potentials appeared postoperatively in 5 patients, 4 of whom had suffered perioperative myocardial infarction. The recordings became normal at the 5th month in 2 of these 5 patients. Holter monitoring at the 5th month compared with a control group, showed a significant correlation between left ventricular potentials and frequent repetitive or polymorphic ventricular extrasystoles. The 40 month survival rate was excellent: 2 patients were lost to follow-up; there were 3 cardiac deaths, one of which was sudden and 4 non-cardiac deaths. All patients with late ventricular potentials were still alive. These results show that late ventricular potentials persist after coronary bypass surgery in 2/3 of patients; their prognostic significance is not obvious. The low incidence of postoperative sudden death could be attributed to the favourable overall effects of revascularisation rather than on the arrhythmogenic substrate.

Adult↗
PubMed1991

[Unwanted cardiovascular effects of anti-arrhythmia agents].

Antiarrhythmic drugs can cause many undesirable side effects affecting a number of organs and functions. Of those which affect the cardiovascular system, the proarrhythmic and negative inotropic effects are the most serious. Proarrhythmic effects, suggested by an aggravation of an arrhythmia or the induction of a previously undocumented arrhythmia, may be favorised by the presence of an arrhythmogenic substrate (unidirectional lock, delayed conduction, dual conduction pathways, low thresholds of depolarisation or fibrillation, presence of zones of hyperautomaticity...), "triggering" mechanisms (extrasystoles, variations of heart rate, after-depolarisation) and by changes in the cardiac environment (variations of autonomic nervous tone and hormonal changes, electrolytic or metabolic disorders...). An antiarrhythmic may have a beneficial action on one of these factors (for example, suppression of extrasystoles) but an aggravating effect on others (for example, an increase in the heart rate, creation of zones of reentry). This probably explains the fact that, for the moment, only molecules which have multifactorial modes of action have been shown to be beneficial in arrhythmias after myocardial infarction. Negative inotropic effects may be directly responsible for a deterioration in the hemodynamic status of patients on antiarrhythmics and indirectly responsible for aggravating arrhythmia by altering the anatomical substrate, so favorising proarrhythmic effects. The negative inotropic action may be related to ionic mechanisms (lowering intracellular calcium concentration due to blockade of the sodium channel by Class I antiarrhythmics) or to indirect mechanisms (reduced sympathetic tone, non-specific beta inhibition, calcium channel blockade, decreased left ventricular compliance, vasoconstrictor effects...).(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Arrhythmia Agents↗
PubMed1990

Hepatitis B-like infection in a Pacific white-sided dolphin (Lagenorhynchus obliquidens).

A Pacific white-sided dolphin (Lagenorhynchus obliquidens) developed clinical signs, serum biochemical values, and serologic viral markers consistent with chronic persistent hepatitis caused by a hepatitis B-like virus. The hepatitis had a sporadic cyclical pattern of lethargy, inappetance, and icterus, with leukocytosis and increased serum activities of alanine transaminase, aspartate transaminase, and gamma-glutamyltransferase. The serum from this dolphin contained hepatitis B virus core antibodies, hepatitis B surface antibodies, and hepatitis B viral DNA. Supportive treatment consisted of administration of antibiotics, cimetidine, menadiol sodium diphosphate, and vitamin/dextrose supplementation. A clinically normal killer whale (Orcinus orca) housed in the same pool had serum hepatitis B surface antibodies, suggesting immunologic responsiveness and that this disease was not species-specific.

Animals↗
PubMed1990

In-vitro and in-vivo electrophysiologic effects of encainide.

The intracellular electrophysiologic effects of encainide (E) and its main metabolite, O-desmethyl-encainide (ODE), were studied in guinea-pig papillary muscle preparations and related to the in-vivo electrophysiologic effects observed after intravenous (IV) infusion of E in 11 patients undergoing electrophysiologic study (EPS). At equipotent concentrations of E and ODE, frequency-dependent reductions in Vmax studied at pacing rates of 30-180 beats/min ranged from -11.5% to -53%, with maximum reductions of -53% and -47%, respectively at the highest frequency. The kinetics of onset of use-dependent Vmax reduction were slower for ODE than for E at each studied pacing rate. The kinetics of total recovery from use-dependent block were still slower (120 seconds for E and 300 seconds for ODE at a 90 beats/min pacing rate). These in-vitro electrophysiologic data could explain the marked alterations in intraventricular and atrioventricular conduction observed in humans 60 minutes after IV administration of 1 mg/kg of E over a 15-minute period. The QRS, PA, AH, and HV intervals were significantly increased (p less than 0.01) and the Wenckebach cycle length was increased by 8% (p less than 0.05). Blood pressure, RR, QT, CSNRT, ESACT, ERP, and FRP did not vary significantly. The HV interval was already increased 2 minutes after drug administration, while AH was not increased until 15 minutes after drug administration. There was a positive correlation between the increase of the AH interval and the blood level of ODE.

Anilides↗
PubMed1990

Effects of skin preapplication treatments and postapplication cleansing agents on dermal absorption of 2,4-dichlorophenoxyacetic acid dimethylamine by Fischer 344 rats.

Various methods of preparing dermal application sites in Fischer 344 rats prior to exposure to 2,4-dichlorophenoxyacetic acid dimethylamine salt (2,4-D amine) and the effect of various cleansing agents following exposure were examined by measuring recoveries of 14C-labeled 2,4-D amine in skin, postapplication cleansing solution, blood, and urine. The middorsal area of the rat was the site of application for four treatments tested: (1) hair clipping only, (2) hair clipping followed by an epilatory cream, (3) hair clipping plus shaving with an electrical razor, and (4) as in treatment 3 followed by washing with soap and water. A last preparation was the rat's tail thoroughly brushed with soap and water. The results indicated that the tail retained greater than 75% of the material, thus preventing its absorption into the blood stream and subsequent removal by cleansing. With treatment 1 the dense short hair remaining after clipping impaired the absorption of 2,4-D as evidenced by considerably lower blood and urinary levels than treatments 2-4. With preparations 1-4, 45-61% of the dose was removed with the 7-h postapplication cleansing and a further 5-6% with the subsequent 23-h cleansing. In other studies using preparation 3 above, the following cleansing agents were tested: soap and water, water, isopropanol, acetone, and Rad-Con, a foam-producing cleanser. Rad-Con removed more 2,4-D from the skin than other cleansing agents after 7 h of exposure and more than soap and water after 23 h. The percentages of 2,4-D left on the skin following either 7- or 23-h cleansing with Rad-Con were 8-12%, nearly half those following the other cleansing agents. Cleansing agents other than Rad-Con presented little advantage over soap and water. With all cleansing agents, delaying cleansing from 7 to 23 h after exposure resulted in higher blood and urinary levels of 2,4-D measured 24 h after application.

1-Propanol↗
PubMed1990

Association of rns homologs with colonization factor antigens in clinical Escherichia coli isolates.

rns is a trans-acting positive regulatory factor required for expression of the colonization factor antigen II (CFA/II) antigens CS1 and CS2 (J. Caron, L. M. Coffield, and J. R. Scott, Proc. Natl. Acad. Sci. USA 86:963-967, 1989). All 35 CFA/II-positive strains hybridized with a rns gene probe, as did all 10 CFA/I strains and all 4 CS4 strains. Hybridization with rns was detected in 25% of non-enterotoxigenic Escherichia coli strains and was not detected in enteric pathogens with low G + C content.

Antigens, Bacterial↗
PubMed1990

A rns-like regulatory gene for colonization factor antigen I (CFA/I) that controls expression of CFA/I pilin.

Colonization factor antigens (CFA) are needed for adherence of human enterotoxigenic Escherichia coli (ETEC) strains to their hosts. The CFA/II antigens, CS1 and CS2, which are found in some ETEC strains, require the plasmid-encoded gene rns for expression (J. Caron, L. M. Coffield, and J. R. Scott, Proc. Natl. Acad. Sci. USA 86:963-967, 1989). Other ETEC strains express CFA/I, whose synthesis and assembly require genes on two unlinked regions (regions 1 and 2) of a plasmid (G. A. Willshaw, H. R. Smith, and B. Rowe, FEMS Microbiol. Lett. 16:101-106, 1983). We report that CFA/I region 2 DNA can substitute for rns to cause expression of CS1 and CS2. The cfaR gene in region 2 is defined by a mutation abolishing both expression of CFA/I and complementation of a rns mutant for expression of CS1 or CS2. In a strain containing only region 1, complementation for expression of CFA/I by a plasmid containing rns+ is inefficient but is adequate to cause hemagglutination by the CFA/I adhesin.

Antigens, Bacterial↗
PubMed1989

A plasmid-encoded regulatory gene, rns, required for expression of the CS1 and CS2 adhesins of enterotoxigenic Escherichia coli.

To be virulent, enterotoxigenic Escherichia coli (ETEC) must produce a toxin and a pilus-like structure that mediates specific attachment to host tissue. Expression of two of these specific adherence structures, CS1 and CS2, requires the presence of a plasmid in an ETEC strain of a particular serotype and biotype. We show here that this plasmid does not contain the structural gene for a pilin protein, as previously believed. Instead we have identified a plasmid-encoded gene called rns that is required for expression of CS1 or CS2 colonization factor antigens and for adhesion. The rns gene, defined by two separately isolated insertion mutations, produces a 26-kDa protein when transcribed and translated in vitro. At the protein level the rns gene product is homologous to AraC, a positive regulator of the arabinose operon of enteric bacteria, and to RhaR and RhaS, which regulate the rhamnose operon of E. coli. The homology of the Rns protein to AraC is localized to regions that are believed to bind to DNA. Moreover, the sequence of one of these homologous regions is consistent with a DNA binding helix-turn-helix motif. The average G + C content of E. coli DNA is 50%; yet the rns gene contains only 28% G + C, suggesting that it was acquired from some other organism.

Adhesins, Escherichia coli↗
PubMed1989

Disposition of 2,4-dichlorophenoxyacetic acid dimethylamine by Fischer 344 rats dosed orally and dermally.

The dimethylamine salt of 14C-ring-labeled 2,4-D was administered to Fischer 344 rats orally (1 and 0.4 mg/kg body weight) and dermally (10 mg/kg body weight). Absorption, distribution, and elimination were determined from 14C-labeled 2,4-D in blood, tissues, and excreta. Quantitatively, most of the orally administered dose (94-96%) became systemically available within 6 h. Following dermal administration 10% of the dose became systemically available over 72 h. However, peak concentrations in blood and kidneys were achieved within 30 min of dosing by either route. By 1.5 h after dosing, 2,4-D concentrations in blood, muscle, liver, and kidneys had decreased in both the orally dosed and dermally dosed animals. Between 2 and 8 h, the blood, muscle, liver and kidney concentrations in dermally dosed animals maintained a plateau while urinary excretion increased, presumably due to continued absorption of 2,4-D from the skin. The concentrations in orally dosed animals continued to decrease. Following 7 h of dermal exposure, skin cleansing removed about 63% of the applied dose; about 17% of the applied dose remained at the site of dermal dosing. At 8 h, 2,4-D concentrations in blood, muscle, liver, and kidneys of dermally dosed animals began to decrease, most likely a result of the removal of the reservoir on the skin. However, 2,4-D continued to be absorbed from skin site, resulting in a slower decline of the 2,4-D concentrations in these tissues over remainder of the 72-h study period. By comparison, in animals that had been orally dosed, the absorbed dose was almost completely excreted within 24 h.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1989

[The visual field of patients with pituitary adenoma surgically treated].

The authors report the evolution of 72 patient's visual field operated for one pituitary adenoma. They specify the constant amelioration of this investigation in chromophobic adenomas. The stability in prolactinic adenomas or somatotropic. Allowing the supervision of the visual case, at these patients, the visual field does not seem useful in the diagnosis of the tumors recurrence.

Adenoma↗
PubMed1989

[Effects of subcutaneous administration of sandostatine (SMS 201.995) in 18 cases of thyroid medullary cancer].

Recent studies have suggested that somatostatin could reduce calcitonin plasma levels (CT) in normal subjects and in medullary thyroid carcinoma (MTC). The aim of this study was to examine the usefulness of the somatostatin analog, sandostatine (SMS 201.995) in MTC with elevated residual CT levels post-thyroidectomy with or without metastases. 18 patients (17-64 years, 12 men and 8 women) with CT greater than 850 pg/ml (N less than 150 pg/ml) and with metastases in 12 cases, were studied. MTC was sporadic in 11 cases, familial in 4 cases and of undefined form in 3. Initial posology was 300 micrograms/d of sandostatin (3 injections/day). It was then increased by 300 micrograms/d every 9 day till a maximum of 1500 micrograms/d. Treatment duration was 37 days in 11 cases and 60 days in 7 cases. Plasma CT and carcinoembryonic antigen levels (CEA) were measured before treatment and at the end of each dosage plateau. Morphologic evaluation of metastases was done at 0, 30, 60 days. 7/18 patients were reevaluated 2 to 8 months after with drawal of sandostatine. Treatment was well tolerated. Flushes improved in 4 out of 5 cases but diarrhea in only 2 out of 9 patients. Sandostatine was without any effect on plasma CEA. Heterogenous responses were observed for plasma CT levels (CT decreases greater than 20% in 8/18 patients when 900 to 1500 micrograms/day were administered). Patients were subdivised into 3 groups according to CEA levels and presence or absence of metastases. Group A (n = 9) had elevated CEA levels (greater than 10 mg/ml) and metastases.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

[Value of determining dexamethasone in the rapid adrenal suppression test].

During the dexamethasone suppression test (DST), we evaluated the relationship between the 8 a.m. dexamethasone (DXM) level and the pharmacokinetics of this corticoid after the oral administration of a single dose at midnight of DXM (1 mg) in 7 healthy subjects. The half-life time of the terminal phase for DXM was 283 min +/- 132 min (mean +/- s.d.). The 8 a.m. DXM level, which is positively correlated with the DXM half-life time, is useful for the interpretation of the DST. On the other hand, no correlation was observed between the 8 a.m. plasma cortisol and DXM levels in 21 healthy subjects. However, the negative correlation between the dose of DXM/kg and post-DXM cortisol level suggests the possibility of adjusting the dose of DXM in obese patients.

Administration, Oral↗
PubMed1988

[Postero-medial bulbar hematoma with a favorable outcome. Study of dysautonomia].

A case of postero-medial medullary hematoma in a 21 year-old woman is reported. An initial neurovegetative severe disregulation had a favorable outcome after surgery. Late deficits, characterizing the postero-medial medullary syndrome have been studied: paresis of the tongue, suppression of the nauseous reflex, instability with retropulsion, and downbeating nystagmus in primary position of the eyes were noted. Heart rate and arterial blood pressure analysis showed explosive tachycardic reactions and transitory disappearance of oculo-cardiac reflexes, suggesting the involvement of the efferent parasympathetic system coming from the dorsal motor nucleus of the vagus nerve.

Adult↗