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Biomedical subjects

C Simon

Publications and source records attributed to C Simon.

At least 217 records · Page 12Linked to original sources
PubMed1990

[Immunohistology of polyps of the nose and paranasal sinuses. Physiopathologic value].

The pathophysiology of nasal polyposis is yet unclear, but chronic disturbances of the inflammatory pathways may be suspected. Immunological investigations were performed in 3 series of patients: 37 with nasal polyps, 22 with chronic sinusitis, and 15 controls with healthy nasal and sinusal mucosa. Patients with nasal polyps had up to ten times more eosinophil density than patients with sinusitis or healthy mucosa. The average of mast cells and IgE or IgA, M, G plasma cells were not different in the various group. Deposited immune complexes were always absent. These results gave us the opportunity to discuss recent pathogenic theories.

Adolescent↗
PubMed1989

Mechanism of GTP hydrolysis in tubulin polymerization: characterization of the kinetic intermediate microtubule-GDP-Pi using phosphate analogues.

Beryllium fluoride (BeF3-) has previously been shown to bind tightly to microtubules as a structural analogue of Pi and to mimic the GDP-Pi transient state in tubulin polymerization [Carlier, M.-F., Didry, D., Melki, R., Chabre, M., & Pantaloni, D. (1988) Biochemistry 27, 3555-3559]. The interaction of BeF3- with tubulin is analyzed here in greater detail. BeF3- binds to and dissociates from microtubule GDP subunits at very slow rates (k+ congruent to 100 M-1 s-1; k- congruent to 6 x 10(-4) s-1), suggesting that a slow conformation change of tubulin, linked to the stabilization of the microtubule structure, follows BeF3- binding. The possibility is evoked that BeF3- acts as a transition-state analogue in the GTPase reaction of tubulin. BeF3- does not bind to dimeric nor to oligomeric GDP-tubulin with high affinity. Substoichiometric binding of BeF3- to microtubules provides extensive stabilization of the structure. An original mechanistic model that accounts for the data is proposed. The kinetic parameters for microtubule elongation in the presence of GTP- and GDP-tubulin with and without BeF3- have been determined. Data support the following views: (i) Microtubules at steady state and in a regime of slow growth in the presence of GTP are stabilized by a cap of GDP-Pi subunits functionally similar to GDP-BeF3 subunits. (ii) In the presence of BeF3-, microtubules elongate from GDP-tubulin within the following sequence of reactions: initial nonproductive binding of GDP-tubulin to microtubule ends is followed by the binding of BeF3- and the associated conformation change allowing sustained elongation.

Animals↗
PubMed1989

Bacteriological findings after premature rupture of the membranes.

Of 243 children born after premature rupture of the membranes (PROM) 61 (26%) had the same bacteria in placental arterial blood, in ear swabs (taken deep from the external auditory canal) and in meconium. The predominant organisms were E. coli, Bacteroides fragilis, Streptococcus faecalis (enterococci) and Streptococcus agalactiae (group B streptococci). The infection rate was only 10% if the membranes had ruptured within 24 h of the onset of labour and 30% if the interval was longer than 24 h. Of 131 children born without premature rupture of the membranes but with risk factors for sepsis 9 (7%) had a positive blood culture with the same organism in the ear swabs and in meconium. The organisms were Streptococcus agalactiae (6 cases) and E. coli, Streptococcus faecalis and Klebsiella pneumoniae (one case each). Contamination of placental blood cultures was rare.

Blood↗
PubMed1989

[Vaginal endosonography in extrauterine pregnancy].

The real value of vaginal sonography in the early diagnosis of ectopic pregnancy was assessed in 12 cases where ectopic pregnancy was suspected by clinical evolution and levels of B-HCG, and subsequently confirmed by microlaparotomy. The results were compared with those obtained with abdominal sonography and values of B-HCG. Vaginal sonography gave no false negatives and the percentage of false positives was 16.6%. The most typical echographyc images were: 1. Adnexal Mass (50%), 2. Pseudoring (42%), 3. Yolk sac &/or Embryo &/or Heart rate (25%). Values of B-HCG greater than 600 mIU/IS without embryo from 35th day are highly suspicious with regard to ectopic pregnancy.

Adult↗
PubMed1989

Amplification of nocturnal oscillations in PRA and aldosterone during continuous heat exposure.

To assess the effect of continuous heat exposure on the nocturnal patterns of renin, aldosterone, adrenocorticotropic hormone (ACTH), and cortisol, six young men were exposed to thermoneutral environment for 5 days, followed by a 5-day acclimation period in a hot dry environment (35 degrees C). Blood was collected at 10-min intervals during the second night at thermoneutrality (N0) and during the first (N1) and the last (N5) nights of heat exposure. Polygraphic recordings of sleep were scored according to established criteria. Continuous heat exposure led to progressive decreases in the 24-h urinary volume and in Na excretion, whereas urinary osmolality increased. After 5 days of uninterrupted heat, significant increases were found in plasma volume (P less than 0.05), osmolality (P less than 0.01), plasma Na (P less than 0.01), and protein levels (P less than 0.05). Sweat gland output increased during the first 3 days and then declined without any concomitant increases in body temperature. Compared with N0, there were no differences in plasma renin activity (PRA) and aldosterone (PA) profiles during N1 at 35 degrees C. However, during N5 the mean PRA and PA levels were significantly (P less than 0.05) enhanced, and their nocturnal oscillations were amplified (P less than 0.05). This amplification occurred mainly in the second part of the night when regular rapid-eye-movement and non-rapid-eye-movement sleep cycles were observed, leading to a general upward trend in the nocturnal profiles. The relationship between the nocturnal PRA oscillations and the sleep cycles was not modified. ACTH and cortisol patterns were not affected by continuous heat exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

Acclimatization↗
PubMed1989

Immunohistological characteristics of nasal polyps. A comparison with healthy mucosa and chronic sinusitis.

Immunohistological investigations were performed on a series of samples from 37 patients with nasal polyps, 22 with chronic sinusitis, and 15 controls with healthy nasal and sinusal mucosa. Mean numbers of plasma- and mast cells were not different in the various groups. Immunoglobulin isotypes were always predominantly IgA and IgM; IgE were scarce. Deposited immune complexes were always absent. A statistically significant difference, however, was observed in the number of eosinophils within the mucosa. Patients with nasal polyps had up to ten times more eosinophils per surface unit than patients with sinusitis or healthy mucosa.

Adolescent↗
PubMed1989

The os in os appearance in the spine and pelvis of adults.

Three cases of radiodense lines contained within bone and coursing parallel to the bony surfaces in skeletally mature patients are discussed. These lines were found to be distinct with normal appearing bone on either side and formed a miniature model of the present bony structure. This "bone within a bone" appearance was discovered on roentgenograms of patients with no history of musculoskeletal disorders. This radiologic finding probably represents a time-limited insult to the immature skeleton and appears to have no clinical significance.

Adult↗
PubMed1988

[Disorders of plasma trace elements in diabetes. Relation to blood glucose equilibrium].

The influence of glycaemic control and diabetes characteristics on plasma concentrations of magnesium, zinc, copper, selenium, rubidium and bromine has been evaluated in 44 diabetics (30 insulin-dependent, 14 non insulin-dependent), and the results obtained were compared to those of 309 control subjects of the same mean age. Diabetics had reduced plasma magnesium concentrations (P less than 0.01) but normal erythrocyte magnesium levels. Plasma zinc and selenium concentrations were reduced, whereas those of copper were increased and those of bromine and rubidium were normal. Correlation between glycaemic control, evaluated by measurement of glycosylated haemoglobin levels, and each of the parameters studied was only demonstrated with magnesium in insulin-dependent diabetics (r = -0.561; P less than 0.02). No correlation was found with the other clinical or anthropometric characteristics of the diabetic patients studied. Diabetes seems to be associated with numerous abnormalities of plasma trace elements and magnesium, but the mechanism of these abnormalities has not yet been elucidated. A decrease in zinc and selenium concentrations and an increase in copper concentrations might be additional factors of atherogenicity.

Adult↗
PubMed1988

Intestinal ammonium production in the rat: the role of the colon, small intestine, and circulating glutamine.

The intestinal ammonium production and the intestinal uptake of circulating glutamine were investigated in anesthetized intact rats and rats with resected small intestine or colon by simultaneous measurements performed on portal and arterial blood. It was shown that ammonium release into the portal blood by the small intestine is of equal magnitude to that released by the colon, and that circulating glutamine participates in ammonium production by the small intestine. Increased levels of circulating glutamine induced by its i.v. infusion to intact rats were not accompanied by an increase in intestinal ammonium production.

Ammonia↗
PubMed1988

Nocturnal fluctuations of plasma atrial natriuretic peptide in normotensive and hypertensive men.

Plasma levels of immunoreactive atrial natriuretic peptides (ANP) were measured at 10-min intervals during night-sleep in 4 normotensive and in 4 moderate, essential hypertensive subjects. The mean ANP levels ranged from 24.3 to 27.9 pg.ml-1 for the normal subjects. These mean levels were not significantly different in the hypertensive subjects (range: 26.3 to 37.2 pg.ml-1). Fluctuations, often of small amplitude, were observed around this mean, without any defined periodicity. Changes in plasma ANP were not associated with changes in heart rate. Analysis of the ANP profiles and the concomitant sleep stage patterns did not reveal any temporal relationship between ANP fluctuations and specific sleep stages or waking periods. The ANP profiles did not differ between the groups, which indicates no abnormality in ANP secretion in moderate essential hypertension.

Adult↗
PubMed1988

Nocturnal oscillations in plasma renin activity and REM-NREM sleep cycles in humans: a common regulatory mechanism?

To establish the strength of the relationship between the nocturnal oscillations in plasma renin activity (PRA) and the sleep stage patterns, 42 PRA profiles from blood collected at 10-min intervals and the concomitant polygraphic sleep recordings were analyzed. In all cases, PRA curves exactly reflected the pattern of sleep stage distribution. When sleep cycles were complete, PRA levels oscillated at a regular 100-min period, with a strong spectral density. Declining PRA levels always coincided with REM sleep phases and increasing levels with NREM sleep phases. More precisely, peak levels corresponded to the transition from deep sleep stages toward lighter ones. The start of the rises in PRA generally marked the transition from REM sleep to stage 2. For incomplete sleep cycles, PRA curves reflected all disturbances and irregularities in the sleep structure. Spontaneous and provoked awakenings blunted the rise in PRA normally associated with NREM sleep, which indicates that disturbing sleep modifies the renin release from the kidneys. These results suggest that a common mechanism within the central nervous system controls both PRA oscillations and the REM-NREM sleep alternation.

Adult↗
PubMed1988

Absence of the dawn phenomenon in normal subjects.

The existence of the dawn phenomenon, defined as an increase in plasma glucose levels and/or insulin requirements in the early morning hours, is well established in diabetic patients but remains controversial in normal subjects. To verify whether this phenomenon occurs in normal subjects, the nocturnal profiles in plasma glucose, insulin, and C-peptide levels; insulin to glucose ratio; and prehepatic insulin production were studied at short intervals (4 and 10 min) in 10 normal men. The first part of the night was characterized by a decrease in all values and the presence of 1 or 2 postprandial fluctuations, followed by a steady state until 0800 h. The individual profiles were frequently superimposable, with rapid 8- to 14-min oscillations. These results do not indicate the existence of a dawn phenomenon in normal subjects.

Adult↗
PubMed1988

REM sleep in humans begins during decreased secretory activity of the anterior pituitary.

The purpose of this study was to define the temporal relationship between anterior pituitary hormone profiles and rapid-eye-movement (REM) sleep occurrence. Plasma levels of prolactin (PRL), adrenocorticotropic hormone (ACTH), luteotropin (LH), thyroid-stimulating hormone (TSH) and growth hormone (GH) were measured in 10 min blood samples. Analysis of the nocturnal profiles for these hormones and the concomitant patterns of sleep stage distribution indicate that the onset of REM sleep very seldom occurred during the increasing phase of secretory episodes. In 93-98% of cases, depending on the hormone studied, it occurred either during the declining phase, at peak level, or at nadir, each of these phases reflecting a decrease in glandular activity. This relationship differed from the very close association previously found between the sleep stage alternation and plasma renin activity. These findings seem to fit in with the concept of reduced sympathetic activity and disruption of the vegetative functions during REM sleep.

Adrenocorticotropic Hormone↗