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Biomedical subjects

C Caron

Publications and source records attributed to C Caron.

At least 37 records · Page 2Linked to original sources
PubMed1989

Triggering of allostery in an enzyme by a point mutation: ornithine transcarbamoylase.

The origin of allostery is an unanswered question in the evolution of complex regulatory proteins. Anabolic ornithine transcarbamoylase, a trimer of identical subunits, is not an allosteric enzyme per se. However, when the active-site residue arginine-106 of the Escherichia coli enzyme is replaced with a glycine through site-directed mutagenesis, the resultant mutant enzyme manifests substrate cooperativity that is absent in the wild-type enzyme. Both homotropic and heterotropic interactions occur in the mutant enzyme. The initial velocity saturation curves of the substrates, carbamoyl phosphate and L-ornithine, conform to the Hill equation. The observed cooperativity depends on substrate but not enzyme concentration. The finding underscores the possibility that a single mutation of the enzyme in the cell could turn transcarbamoylation into a regulatory junction in the biosynthesis of L-arginine and urea.

Allosteric Regulation↗
PubMed1989

Stuttering severity and treatment outcome.

This study evaluated a multidimensional treatment of stuttering (awareness training, regulated breathing, cognitive restructuring and relapse prevention) for mild, moderate and severe stutterers. Behavioral measures (percentage of syllables stuttered and rate of speech) and cognitive measures (self-efficacy perception, locus of control and Erickson Scale) were taken. Using three multiple baseline designs across subjects, results showed that all mild stutterers and most moderate stutterers were clinically improved at the end of treatment and at six months follow-up. No severe stutterers (more than 15% of syllables stuttered) achieved clinical improvement. Self-efficacy perceptions were quite accurate in predicting the performance of successfully treated patients. No consistent changes were observed on the locus of control or the Erickson Scale. The clinical and theoretical implications of the results are discussed.

Adaptation, Psychological↗
PubMed1989

Isolation and characterization of monoclonal antibodies against alkaline phosphatase of Pseudomonas aeruginosa.

Monoclonal antibodies against the alkaline phosphatase of Pseudomonas aeruginosa were produced from spleen cells of BALB/c mice primed with purified alkaline phosphatase of P. aeruginosa ATCC 10145 and SP20/Ag-14 myeloma cells. The eight stable clones established produced antibodies that reacted by enzyme-linked immunosorbent and indirect immunofluorescence assays with all bacterial strains of P. aeruginosa, including the 17 serotypes and two nontypable strains. Three of the clones cross-reacted only with some Pseudomonas species of the rRNA homology group I defined by N. J. Palleroni (in N. R. Krieg and J. G. Holt, ed., Bergey's Manual of Systematic Bacteriology, 8th ed., p. 140-218, 1984). The other clones also interacted with other species, including Pseudomonas acidovorans and Xanthomonas maltophilia. Because other species of the genera Aeromonas and Acinetobacter and species of the family Enterobacteriaceae were not detected by these monoclonal antibodies, the antibodies could be used as reagents for routine detection of P. aeruginosa in clinical specimens. Interactions of the antibodies with other Pseudomonas species such as P. fluorescens and P. stutzeri are not important, since these species are susceptible to the same antipseudomonal agents.

Alkaline Phosphatase↗
PubMed1989

[Predicting factors of adjustment to chronic hemodialysis: review of the literature and future prospects].

Little is yet known about predictive factors of adjustment to hemodialysis. This paper reports on a review of 45 articles published between 1966 and 1986, and focused on three issues: (1) the definition of the adjustment to chronic hemodialysis according to compliance, social and vocational rehabilitation and psychological adjustment; (2) the way adjustment is objectively and subjectively evaluated; (3) the predictive factors of a good adjustment to hemodialysis which are: an internal locus of control, defense mechanisms such as denial, repression and projection, and family factors as a good parental relationship and optimistic and positive interactions. Demographic factors (age, sex, education, IQ) are not found to be associated with adjustment. In conclusion, the author derives from the literature four specific landmarks for future research.

Adaptation, Psychological↗
PubMed1988

Acquired type II von Willebrand's disease: demonstration of a complexed inhibitor of the von Willebrand factor-platelet interaction and response to treatment.

An acquired von Willebrand's disease developed in two patients in association with a monoclonal gammopathy plus a Sjögren's syndrome and a chronic lymphocytic leukaemia (CLL). In both cases a plasma inhibitor to von Willebrand factor (vWf) was suspected and characterized after plasma gel filtration. The inhibitor was shown to be entirely complexed with vWf and was only demonstrated after complex dissociation by heating. The inhibitor was able to inhibit the binding of 125I-vWf to platelets in the presence of ristocetin in both cases and to thrombin-stimulated platelets in one case. In the two patients, the highest molecular weight multimers (HMWM) of vWf were absent when assessed by sodium dodecyl-sulphate agarose plasma electrophoresis. Intravenous infusion of 1-deamino-(8-D-arginine) vasopressin (DDAVP) resulted in the appearance of the HMWM in both cases and of the satellite bands of each multimer subunit which were lacking prior to the infusion in one patient. After transfusion of a VIII/vWf concentrate containing a significant amount of HMWM, there was a rapid plasma clearance of the vWf-related activities and of the HMWM when compared to that seen in a patient with type III constitutional vWD. We conclude that in the two patients studied the coagulation defect was related to the presence of a circulating inhibitor to vWf which could be responsible for the disappearance of the HMWM from plasma.

Aged↗
PubMed1988

Lupus anticoagulant: a clinical and laboratory study of 100 cases.

The clinical and laboratory features of 100 patients with lupus anticoagulant (LA) are reviewed. Subjects were divided into three groups according to their age (1-5, 15-35, 45-89 years). Female prevalence was observed in each group and overall F/M ratio was 3/1. An underlying autoimmune disease (principally lupus erythematosus) was found in 47 cases (10% of the children, 80% of the 15-35-year-old patients and 37% of the elderly patients). Biological criteria for the LA diagnosis were prolonged activated partial thromboplastin time and diluted thromboplastin time (1.3 x control), not corrected after addition of control to patient's plasma. Thromboplastin time was normal in 77 patients. Other types of coagulation inhibitors were eliminated by specific factor assays (with a 10-fold increase of cephalin concentration when necessary). Twenty-three thrombotic episodes were observed. No significant difference was found in the incidence of thrombosis between the autoimmune and non-autoimmune disease group, but the age when first thrombosis occurred was clearly lower in the former. Fourteen obstetrical accidents were noted in eight women but 13 pregnancies terminated without accident. Four patients experienced haemorrhagic complications; they all presented with a severe thrombocytopenia associated with the LA. In our experience, LA is a frequent coagulation abnormality, associated in about half of the cases with a clearly defined autoimmune disease. Clinical presentation appears as notably different according to the patient's age; it is particularly noteworthy that in nine out of 10 children, LA disappeared spontaneously within 6 months.

Adolescent↗
PubMed1988

[Chronic aortic dissection disclosed by pericardial effusion. Apropos of 3 cases].

Three exceptional cases of chronic aortic dissection revealed by a pericardial effusion are reported. The patients were two men and a woman admitted for thoracic pain or fever. Initial diagnoses were myocardial infarction, infective endocarditis and tuberculous pericarditis. The effusions were drained on two occasions. Because the pericardial fluid was a mixture of serum and blood, computerized tomography of the thorax and abdomen was performed. All three cases were then diagnosed as aortic dissection (type II in two cases and type III in one case, with retrograde extension to the ascending aorta). The authors underline the utility of drainage and the need for systematic CT scans in patients with sero-haematic pericardial effusion of uncertain origin.

Aged↗
PubMed1987

[Severe pulmonary embolism disclosing a deficiency in protein C].

A constitutional deficit in protein C is a rare disorder. Our report concerns a 35 year old non-smoking male, presenting with a past history of uncomplicated phlebitis of the lower limbs. In the course of a new episode of phlebitis, the patient presented with a severe pulmonary embolus treated by embolectomy under extracorporal circulation, with interruption of the inferior vena cava. The plasma level of protein C (Elisa technique) measured before treatment with antivitamin K was 40% (normal 70-140%). The absence of associated hepatic or haematological anomalies confirmed the constitutional character of the deficit. The immediate and subsequent progress turned out favourably on treatment with heparin, then anti-vitamin K.

Adult↗
PubMed1987

[Silent aortic insufficiency mimicking dilated cardiomyopathy].

The authors report 6 cases of severe and silent aortic insufficiency having simulated in all aspects the picture of a dilated cardiomyopathy at the stage of cardiac insufficiency with primary manifestations. They insist on signs leading to the diagnosis of this clinical entity: past history of rheumatism, signs of electrical left ventricular hypertrophy in the absence of arterial hypertension, aortic calcifications and mostly presence of a discrete mitral diastolic fluttering during echocardiographic examination. Supra-sigmoid aortic angiography confirms the diagnosis of severe aortic regurgitation. In order to explain the non-perception of the murmur, they invoke the alteration of the transmission secondary to an air cushion (3 cases the association of another valvulopathy with murmur (1 case) and mainly the decrease of the leakage by increase of the left ventricular telediastolic pressure and the decrease of the diastolic aortic pressure, with diminution of the turbulences. The advantage of knowing this entity rests on the possibility of valve replacement, even at the stage of myocardial failure, since the satisfactory long-term post-operative evolution in 4 patients stands in contrast with the dangerous nature of a spontaneous evolution.

Aortic Valve Insufficiency↗
PubMed1987

The ergometrine test: effects on esophageal motility in patients with chest pain and normal coronary arteries.

Ergometrine can evoke coronary spasm in patients with variant angina. The cause of ergometrine-induced chest pain in the absence of coronary spasm is not clear. To determine whether ergometrine produced esophageal dysfunction and chest pain, we evaluated 28 patients by esophageal manometry. Six had chest pain in response to ergometrine during cardiac catheterization (group I) and 22 did not (group II). Results of cardiac catheterization were normal in all patients. Seven volunteers with no history of chest pain formed a control group (group III). Esophageal manometry was performed before and after ergometrine administration (0.4 mg I.V.). Ergometrine provocation during esophageal manometry caused significant deterioration in esophageal motility associated with familiar pain in 5/6 group 1 patients. The motility disorders were characterized by repetitive contracts of high amplitude and long duration in the distal esophagus. No patient from group II or III experienced chest pain after ergometrine and only 2 from group II developed long duration contractions. Thus, we conclude that in patients with normal coronary angiograms, ergometrine-induced chest pain without associated coronary spasm suggests that esophageal motility disorders originate chest pain.

Angina Pectoris↗
PubMed1986

[Inhibitors of factor VIII in non-hemophilic patients. Biological and therapeutic aspects. Apropos of 3 cases].

A coagulation inhibitor of the anti-factor VIII: C type was detected in three non-haemophilic male patients aged 75, 70 and 52 respectively. In all three patients antibody titres were low (less than 12.5 Bethesda units initially, less than 20 units subsequently), and a low but detectable level of factor VIII: C persisted (7 to 12 p. 100 in two patients who had severe haemorrhages and 2.100 in the third one). The 3 inhibitors inactivated factor VIII: C with a complex, type II kinetics (Biggs et al.). Strong doses of anti-haemophilic A fractions were biologically effective in one patient but could not stop severe bleeding. Activated plasma fractions were used successfully on several occasions. Once, moderate and repeated doses of anti-haemophilic A fractions resulted in satisfactory correction of factor VIII: C level, and a minor surgical operation could be performed. An immunosuppressive treatment was administered for 3 weeks to one patient and for 3 months to the other two patients. In all three cases the inhibitor disappeared after 5 to 8 months. In non-haemophilic patients with factor VII: C inhibitor the treatment of haemorrhagic episodes must take into account the severity of bleeding, then the usually complex kinetics of the inhibitor; thus it cannot be a direct copy of the treatment used in haemophiliacs with type I inhibitors.

Aged↗
PubMed1986

[Successes and failures of the activated partial thromboplastin time in the preoperative evaluation].

In a prospective study assessing haemostatic functions, the activated partial thromboplastin time was prolonged in 134 out of 10,229 patients studied, without an increase in the prothrombin or thrombin times; this abnormality persisted in only 37 of them on a new blood sample. A retrospective analysis was made of 265 patients who had such an isolated prolongation of the activated partial thromboplastin time on two successive blood samples: the causal abnormality remained unexplained in 135 patients; a well defined coagulation disorder without abnormal bleeding tendency was present in 110 patients (1 severe factor XII deficiency, 58 partial factor XI or XII deficiencies and 51 lupus anticoagulants); a bleeding disorder was diagnosed in 20 patients (8 haemophilias, 8 Von Willebrand's diseases, 4 factor VIII inhibitors). The well-iron efficacy of the activated partial thromboplastin time for detecting coagulation abnormalities is counter-balanced by some disadvantages such as the delay for biologic conclusions. In the preoperative assessment of haemostatic functions, rather than taking a routine approach, it would seem better to determine for each patient the need and the extent of biological testing according to the type of planned surgery, the clinical status of the patient and possible bleeding symptoms.

Blood Coagulation Tests↗
PubMed1986

[Maternal complications of cesarean section. Results of a multicenter study. I].

The authors report a study they have made of 7,216 case histories designed to show the type and the number of the various maternal complications of the caesarean operation and compare these results with those found in the literature and those that occur after vaginal delivery. The maternal mortality rate directly associated with the operation is 1.38/000, which is between 5 and 25 times greater than those for vaginal delivery. The pre-operative anaesthetic and surgical complications are rare and are usually not very serious. They depend on the experience of the operators. The post-operative complications tend to be mainly due to infections and thrombo-embolic phenomena. If the most minor infections are included, the infection rate for caesarean operations rises to 20.6%, whereas thrombo-embolic complications are rare at 0.52%.

Cesarean Section↗