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Biomedical subjects

C Simon

Publications and source records attributed to C Simon.

At least 91 records · Page 5Linked to original sources
PubMed1998

Dynamic heart rate variability: a tool for exploring sympathovagal balance continuously during sleep in men.

We have recently demonstrated that the overnight profiles of cardiac interbeat autocorrelation coefficient of R-R intervals (rRR) calculated at 1-min intervals are related to the changes in sleep electroencephalographic (EEG) mean frequency, which reflect depth of sleep. Other quantitative measures of the Poincaré plots, i.e., the standard deviation of normal R-R intervals (SDNN) and the root mean square difference among successive R-R normal intervals (RMSSD), are commonly used to evaluate heart rate variability. The present study was designed to compare the nocturnal profiles of rRR, SDNN, and RMSSD with the R-R spectral power components: high-frequency (HF) power, reflecting parasympathetic activity; low-frequency (LF) power, reflecting a predominance of sympathetic activity with a parasympathetic component; and the LF-to-HF ratio (LF/HF), regarded as an index of sympathovagal balance. rRR, SDNN, RMSSD, and the spectral power components were calculated every 5 min during sleep in 15 healthy subjects. The overnight profiles of rRR and LF/HF showed coordinate variations with highly significant correlation coefficients (P < 0.001 in all subjects). SDNN correlated with LF power (P < 0.001), and RMSSD correlated with HF power (P < 0.001). The overnight profiles of rRR and EEG mean frequency were found to be closely related with highly cross-correlated coefficients (P < 0. 001). SDNN and EEG mean frequency were also highly cross correlated (P < 0.001 in all subjects but 1). No systematic relationship was found between RMSSD and EEG mean frequency. In conclusion, rRR appears to be a new tool for evaluating the dynamic beat-to-beat interval behavior and the sympathovagal balance continuously during sleep. This nonlinear method may provide new insight into autonomic disorders.

Adult↗
PubMed1998

Ultradian pulsatility of plasma glucose and insulin secretion rate: circadian and sleep modulation.

Insulin release is a complex oscillatory process with rapid pulses (10 min) superimposed on slower circhoral oscillations (50-100 min). The exact mechanism of the circhoral oscillations, which are probably in part the consequence of a negative feedback loop linking glucose and insulin secretion rate, remains unclear. Stimulatory effects of sleep on insulin secretion are achieved by an enhancement of the oscillation amplitude which could be partly mediated by GH. The different patterns observed after acute or chronic shift of sleep suggest however an interaction between sleep influence and circadian rhythmicity, as described for numerous pituitary hormones. The intra-sleep awakenings have a modulatory effect on glucose levels but no systematic relationship exists between glucose or insulin secretion rate oscillations and the REM-NREM sleep cycles. Irrespective of the mechanisms involved, sleep or GH stimulatory effects result from a modulation of the oscillation amplitude rather than of their frequency which is probably an important feature of insulin efficacy.

Activity Cycles↗
PubMed1998

Circadian and ultradian variations of leptin in normal man under continuous enteral nutrition: relationship to sleep and body temperature.

To determine the influence of circadian rhythmicity and sleep on the 24-h leptin diurnal variations, plasma leptin levels were measured at 10-min intervals over 24 h in seven normal subjects, once during nocturnal sleep, and once after an 8-h shift of sleep. The subjects were submitted to constant conditions (continuous enteral nutrition and bed rest in controlled chambers). Body temperature and plasma glucose and insulin levels were measured simultaneously. During nighttime sleep, leptin levels increased to a maximum (109.9 +/- 2.5% of the 24-h mean) and then decreased to reach a nadir in the late afternoon. The mean diurnal variation was 18.0 +/- 3.8% of the 24-h mean. In the daytime sleep condition, leptin levels rose during the night of deprivation to a maximum of 104.7 +/- 2.3% of the 24-h mean, decreased to a minimum around 0700 h, and then rose again during diurnal sleep (108.4 +/- 3.1% of the 24-h mean); the mean diurnal variation was 13.4 +/- 3.6% of the 24-h mean. ANOVA revealed a significant interaction between time of day and sleep effects (P < 0.05). The diurnal and the sleep-related variations of plasma leptin mirrored those of body temperature and roughly paralleled those of plasma glucose and insulin; the amplitudes of the diurnal leptin variations were significantly correlated with the amplitudes of the diurnal body temperature variations (P < 0.05). Plasma leptin levels also displayed irregular pulses of low amplitude (mean duration, 70 min) that were not affected by sleep, but were associated with a significant decrease in glucose and insulin levels (P < 0.01). These results demonstrate that under continuous enteral nutrition, plasma leptin levels are modulated by both a slight circadian component and sleep, which interact under normal conditions, and suggest that leptin is implicated in circadian thermoregulatory adjustments.

Adult↗
PubMed1998

[Lipoma of the internal auditory canal. Report of two cases simulating acoustic neuroma].

We report two cases of intra-auditory canal lipoma, presenting as acoustic neuroma, observed in respectively 45 and 53 year old patients. Cerebellopontine angle lipomas are unusual lesions, more exceptional than their intracranial counter-parts. The knowledge of these tumoral lesions and of their close relationships with cranial nerves incite to perform a frozen section when imagery is evocative, to limit functional postoperative sequelae.

Diagnosis, Differential↗
PubMed1998

[Bone anchored hearing aid (BAHA): clinical evaluation].

UNLABELLED: The bone-anchored hearing aid (BAHA) allows direct bone-conduction through a titanium implant. This avoids skin irritation and seems to improve the sound quality when compared with a conventional bone hearing aid. Aim of this work was to evaluate this new hearing-aid. PATIENTS AND METHODS: 9 patients have been operated on between May 1994 and April 1997. Two aural atresia and 7 radical mastoidectomy; 6 had prior conventional bone hearing aid and one a bilateral air-conduction hearing aid. Their mean bone conduction threshold was 28 dB (17-38 dB). Their maximum speech discrimination score was 100%. Audiological tests and questionnaires were used for the evaluation. RESULTS: The mean follow-up was 9-months (3-35). Osseointegration succeeded in the 9 cases. Skin tolerance was excellent in 6 cases. 3 patients had transient adverse skin reactions, with one having needed a revision surgery under local anesthesia. All patients use their BAHA everyday. The mean prosthesis gain was 36 dB (20-50 dB). Eight patients completed the questionnaire. Patients reported an overall satisfaction score between 9 and 10 (range 6-10). BAHA advantageously replaced the prior hearing aid (mean satisfaction score: 9.1 for BAHA versus 5.9). The only complaints were sensitivity to wind noise and lack of a phone connexion.

Adult↗
PubMed1997

Cervical lymph node metastasis from an unknown primary: is a tonsillectomy necessary?

PURPOSE: The detection of an infraclinical primary by tonsillectomy in case of cervical lymph node of an epidermoid carcinoma with unknown primary after a radical neck dissection, allows avoiding irradiation of the normal larynx. The aim of this study is to quantify the rate of tonsil primary to justify this procedure. METHODS AND MATERIALS: From 1969 to 1992, 87 patients had a tonsillectomy as part of the workup for cervical nodal metastasis of an epidermoid carcinoma with unknown primary. The mean age was 57 years (range: 39-75 years) and the sex ratio was 8.6. Sixty-seven patients had a single cervical adenopathy (17 N1, 30 N2a, 5 N3, 15 Nx), and 20 patients multiple cervical adenopathies (17 N2b, 3 N2c). The treatments included always an irradiation to the node areas (50 Gy), and to the pharyngolarynx in case of normal tonsil (50 Gy), or to the tonsil if it was the primary (50 Gy with a brachytherapy boost of 20-25 Gy). In this last case, the larynx could be protected. RESULTS: Tonsillectomy never induced specific complication. Out of 87 patients, 26% had a tonsil primary. There was not specific histological differentiation in this group. In the 67 patients with a single cervical adenopathy, 31% had a tonsil primary (6 N1, 7 N2, 1 N3, 7 Nx). It was a subdigastric adenopathy in 38%, a submandibular in 28% and a midjugulocarotidian in 23%. Among the 17 patients N2b, none had a tonsil primary. In the three patients N2c, two presented a tonsil carcinoma (two subdigastric nodes). CONCLUSION: Tonsillectomy allows avoiding irradiation of normal larynx in 26% of patients who have a cervical lymph node with unknown primary. It should be performed in case of a single node of the subdigastric, midjugulocarotidian or submandibular area or bilateral subdigastric adenopathies.

Adult↗
PubMed1997

Temporal relationship between dynamic heart rate variability and electroencephalographic activity during sleep in man.

In previous sleep studies, it has been demonstrated that Poincare plots of RR intervals, which provide a beat to beat dynamic measure of heart rate variability, have distinctive and characteristic patterns according to sleep stages. This study was designed to evaluate the temporal relationship between heart rate variability and sleep electroencephalographic activity (EEG) by using the Pearson's interbeat autocorrelation coefficients of RR intervals derived from the Poincare plots. The coefficients were calculated in 12 subjects over each minute and were related to the profiles of EEG mean frequency (0.5-35 Hz) computed using a Fast Fourier Transformation algorithm. Overnight profiles of interbeat autocorrelation coefficients and of EEG mean frequency were found to be related with highly significant cross-correlation coefficients ranging between 0.216 and 0.638 (P < 0.001). The variations in heart rate variability preceded changes in brain activity by 1-2 min. These results demonstrate that beat to beat heart rate variability and EEG activity are closely linked during sleep in normal man.

Adult↗
PubMed1997

Elevated urokinase-type plasminogen activator receptor expression in a colon cancer cell line is due to a constitutively activated extracellular signal-regulated kinase-1-dependent signaling cascade.

The urokinase-type plasminogen activator receptor (u-PAR) facilitates extracellular matrix degradation in part by accelerating plasmin formation at the cell surface. We previously reported that u-PAR expression is elevated in colon cancer cell lines characterized by their in vitro invasive capacity. Since, u-PAR expression is increased by a variety of growth factors, which signal through the extracellular signal-regulated kinases 1 and 2 (ERK1/ERK2), we determined if these mitogen-activated protein kinases (MAPKs) regulate u-PAR expression in two cultured colon cancer cell lines. An in-gel kinase assay showed that ERK1 activity was considerably higher in RKO cells, which display > or = 10(5) receptors/cell, than the GEO cells which have approximately 10(4) urokinase receptors per cell. The expression of either an ERK-inactivating phosphatase (CL100), or a kinase-defective ERK1, decreased the activity of a u-PAR promoter-driven CAT reporter in RKO cells. Immune complex kinase assays indicated that the constitutive ERK1 activity in RKO cells was largely a result of an activated MEK1. Further, treatment of RKO cells with a specific inhibitor (PD 098059) of MEK1 activation, which diminished ERK1 activity, reduced the amount of urokinase specifically bound to the cell surface and this was associated with reduced laminin degradation. The expression of a dominant negative c-Raf-1 also reduced u-PAR promoter activity suggesting that MEK1 activation involved an activator at, or upstream, of this serine-threonine kinase. Transfection of the u-PAR-deficient GEO cells with a constitutively activated MEK1 expression construct up-regulated u-PAR promoter activity. Similarly treatment of GEO cells with a phosphatase inhibitor (sodium vanadate) caused a dose-dependent increase in ERK1 activity which paralleled increased cell surface binding of urokinase. Taken together, these data suggest that elevated u-PAR expression, in at least a sub-population of colon cancer, is partly a consequence of a constitutively activated ERK-1-dependent signaling cascade.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1997

Evolution of the mitochondrial cytochrome oxidase II gene in collembola.

The sequence of the mitochondrial COII gene has been widely used to estimate phylogenetic relationships at different taxomonic levels across insects. We investigated the molecular evolution of the COII gene and its usefulness for reconstructing phylogenetic relationships within and among four collembolan families. The collembolan COII gene showed the lowest A + T content of all insects so far examined, confirming that the well-known A + T bias in insect mitochondrial genes tends to increase from the basal to apical orders. Fifty-seven percent of all nucleotide positions were variable and most of the third codon positions appeared free to vary. Values of genetic distance between congeneric species and between families were remarkably high; in some cases the latter were higher than divergence values between other orders of insects. The remarkably high divergence levels observed here provide evidence that collembolan taxa are quite old; divergence levels among collembolan families equaled or exceeded divergences among pterygote insect orders. Once the saturated third-codon positions (which violated stationarity of base frequencies) were removed, the COII sequences contained phylogenetic information, but the extent of that information was overestimated by parsimony methods relative to likelihood methods. In the phylogenetic analysis, consistent statistical support was obtained for the monophyly of all four genera examined, but relationships among genera/families were not well supported. Within the genus Orchesella, relationships were well resolved and agreed with allozyme data. Within the genus Isotomurus, although three pairs of populations were consistently identified, these appeared to have arisen in a burst of evolution from an earlier ancestor. Isotomurus italicus always appeared as basal and I. palustris appeared to harbor a cryptic species, corroborating allozyme data.

Amino Acid Sequence↗
PubMed1997

Increased incidence of disomic sperm nuclei in a 47,XYY male assessed by fluorescent in situ hybridization (FISH).

Using triple-colour fluorescent in situ hybridization in decondensed sperm heads, we assessed the sex-chromosome distribution in spermatozoa from a 47,XYY male compared with controls. The incidence of spermatozoa with 24,XY (0.30%) and 24,YY (1.01%) disomy was significantly higher than in our control series. Diploid meiocytes present in the ejaculate were mainly 47,XYY (60.6-86.7%), and haploid meiocytes were mainly 24,XY (78.1%).These results suggest that, although the extra Y chromosome is thought to be eliminated during spermatogenesis, XYY germ cells can complete meiosis and produce disomic spermatozoa.

Adult↗
PubMed1997

Post-operative brachytherapy: a prognostic factor for local control in epidermoid carcinomas of the mouth floor.

The aim of this study was to analyse the role of post-operative brachytherapy (BT) in a group of patients with a high risk of local relapse (positive or narrow surgical margins) for squamous cell carcinoma of the mouth floor (SCCFM). A comparison with post-operative external beam irradiation (EBI) in a group of patients with standard risk of local relapse for SCCFM with free margins is performed to estimate the benefit of BT. From 1979 to 1992, an initial group of 32 patients with SCCFM (12, T1-2; 20, T3-4x) received an Ir 192 low dose rate BT using plastic tubes (+EBI for 20 patients) after surgery with positive or close margins. BT was applied in one or two planes to the surgical scar. The mean dose of BT was 57 Gy (range: 50-60) for exclusive BT and 22 Gy (range: 15-30) when a boost was applied (mean EBI dose = 50 Gy). During the same period, 36 patients had post-operative external irradiation alone after satisfactory surgical resection. Excluding the post-operative margin, these two groups were comparable for other prognostic factors. The mean follow-up was 46 months (range: 5-145) with a minimum follow-up of 2 years. For BT and EBI groups, the 5-year results (Kaplan-Meier) were, respectively, overall survival 62% and 43%, local control 81% and 60% (P = 0.09) (log-rank) and severe complications 4/32 and 1/36. Post-operative BT achieves good local control for patients with narrow or positive margins by increasing the dose to the surgical scar, with good tolerance. Given these encouraging results, we confirm this treatment for these patients.

Brachytherapy↗
PubMed1997

New nepenthone and thevinone derivatives.

The diastereoselective reaction of thevinone (2a) and nepenthone (2c) and their dihydro derivatives (2b and d) with Grignard reagents afforded new N-substituted (20S)- and (20R)-phenyl-6,14-ethenomorphinan derivatives (6a-y). The Grignard reaction of the N-substituted-N-demethyl derivatives 4a-f and 4m-r with methylmagnesium iodide resulted in the (20R)-phenyl tertiary alcohols 5a-f and 5m-r, respectively, but the conversion of 4g-1 and that of the N-substituted-dihydrothevinone derivatives with phenylmagnesium bromide afforded the (20S)-phenyl derivatives 5g-l and 5s-y, respectively. The N-cyclopropylmethyl-, N-beta-phenylethyl-, and N-propyl derivatives were prepared by the 3-O-demethylation of compounds 5. For the synthesis of the N-allyl-, N-dimethylallyl-, and N-propargyl compounds 2a-d were reacted with the corresponding Grignard reagent, and treatment of the products with cyanogen bromide gave the cyanamides 8a-d. These latter compounds were transformed into 10a, b,d, whose alkylation led to the target derivatives 6d-f, j-l, p-r, and w-y. The biochemical investigation of these substances showed that the affinities to the delta-opioid receptors were high, but the selectivity was low. In two cases (6c and 11d) a mu-opioid receptor specificity was observed.

Animals↗
PubMed1997

[Bipolar radiofrequency energy in arteries--the experimental results with a new catheter system].

PURPOSE: To evaluate the effects of radiofrequency heated bipolar probes on the human arterial wall. METHODS: Under standardised conditions, lesions were set on the inner layer of a piece of human cadaver arterial wall, using a radiofrequency-heated bipolar catheter. These lesions were measured and described both macroscopically and microscopically. Lesion size, applied energy levels and application conditions were correlated. RESULTS: The size of a lesion depended significantly on the size of the catheter, angle and pressure of catheter application (p < 0.05) and length of impulse (p = 0.002). There was no influence from the energy level employed. It proved impossible to treat calcified plaques. The depth of a lesion depended on the angle of catheter application only. No perforations were seen. CONCLUSIONS: Radiofrequency-heated bipolar catheters ablate the tissue of the arterial wall. Increasing tissue resistance resulting from higher energy levels prevents perforation in the experimental set-up. Calcified plaques cannot be treated by this method.

Aorta, Abdominal↗
PubMed1997

[Changes in liver perfusion caused by transjugular intrahepatic stent shunt (TIPSS)].

PURPOSE: to demonstrate and document TIPSS-induced changes of the perfusion pattern of the liver with special reference to several rheologic, morphologic, functional and biochemical parameters. Our analysis was based on a study in 100 consecutive cases. PATIENTS AND METHODS: Evaluation and assessment of the following parameters before and within a 30-day post TIPSS period: portosystemic gradient; morphologic delineation of the portal circulation; invasive scintigraphic determination of the portal perfusion fraction (PPF) and the total liver perfusion (GLP); transcatheter intraarterial flow change measurement; serum levels of albumin and bilirubin; assessment of hepatic encephalopathy by appropriate testing; assessment of recurrent variceal bleeding RESULTS: by TIPSS variceal filling was widely reduced; as assessed morphologically and rheologically portal liver perfusion was significantly reduced. However, there was immediate onset of compensated liver perfusion by increased arterial inflow. Total liver perfusion was not significantly altered. In TIPSS portal decompression was readily achieved with reduction of the portosystemic gradient from an average of 24 mmHg to 10.5 mmHg. In our series we could not demonstrate an increased incidence of hepatic encephalopathy during the 30-day post TIPSS period. Bilirubin levels were significantly increased after TIPSS from 2.45 to 2.61 mg/dl (p = 0.0067), while albumin levels were not altered. Early mortality was 4% and early re-bleeding rate 3%, respectively. CONCLUSION: the concept of TIPSS represents an individually calibrated H-shunt. The significant reduction of post TIPSS portal perfusion appears to be compensated by increased arterial inflow. This is reflected by invasive flow measurement results and by the clinical results. Letality of TIPSS is low.

Blood Flow Velocity↗
PubMed1997

[Anterior frontal laryngectomy without epiglottoplasty or modified Tucker's technique. Proposal for a surgical simplification].

By replacing epiglottic reconstruction with a muscular translation, we attempted to simplify the near total laryngectomy with epiglottic reconstruction and improve swallowing disorders. Ten operated patients were followed up for at least 9 to 22 months. We obtained 9 good results and 1 failure. The long terms results have to be evaluated to assess risk of laryngeal stenosis.

Aged↗
PubMed1997

Terlipressin may influence the outcome of hepatorenal syndrome complicating alcoholic hepatitis.

Hepatorenal syndrome is a frequent complication associated with extremely short survival in cirrhotic patients with alcoholic hepatitis. Vasopressin analogs have been reported to induce transient regression of hepatorenal syndrome in patients with cirrhosis. However, treatment withdrawal was followed by early recurrences in every case. We report the case of a 68-yr-old woman with severe alcoholic hepatitis complicated by hepatorenal syndrome. Terlipressin induced a prolonged recovery of renal function that was associated with improvement in hepatic function.

Aged↗
PubMed1997

[Follow-up of albumin excretion during pregnancy and post partum in type 1 diabetic patients in comparison with health pregnant probands].

32 diabetic and 31 metabolic healthy pregnant women are studied to answer the following questions: Is there a difference in the albumin-excretion rate (AER) during the pregnancy in primary normoalbuminuric type 1 diabetics and non-diabetics? Is there a difference 6 months post partum between the 2 groups? The average age of the diabetics (D) is 28, of the non-diabetics (ND) 27 years; the diabetics suffer from diabetes mellitus 12.5 years. In the 16th week of pregnancy, we find a AER (D vs. ND) of 5.0 vs. 2.37 micrograms/min (not significant [n.s.]), creatinin in serum 0.77 vs. 0.75 mg/dl (p < 0.05), creatinin clearance 92.5 vs. 103.4 ml/min (n.s.). In the 28th and in the 34th to 38th week, there is no significant elevation of the AER compared to the 16th week; but there is a significant elevation in the diabetics vs. the non-diabetics. 6 months post partum, the AER (D vs. ND) are: 6.13 vs. 5.11 micrograms/min (n.s. vs. 16th week and D vs. ND); in each group one person is found with a positive microalbuminuria (MA): 48.2 micrograms/min (D) and 27.4 mg/min (ND). Another diabetic woman shows post partum an isolated higher value of creatinin in serum: 1.5 mg/dl (without MA). This parameter is post partum significant higher (0.97 [D], 0.96 [ND] mg/dl) than in the 16th week of pregnancy (0.77 [D], 0.75 [ND] mg/dl). The creatinin clearance decreases post partum (pp): 92.2 ml/min (pp) vs. 102.0 ml/min (28th week) in the diabetics (n.s.) and 80.6 ml/min (pp) vs. 111.0 ml/min (28th week) in the non-diabetics (p < 0.05). Concerning the studied renal parameters, there is a significant difference of the albumin-excretion rates during the pregnancy between preconceptional normoalbuminuric type 1 diabetic and non-diabetic women, but 6 months post partum, there is no significant difference. The diabetics show a significant increase of the creatinin in urine and in serum and no significant change of the creatinin clearance 6 months post partum.

Adult↗