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Biomedical subjects

C Simon

Publications and source records attributed to C Simon.

At least 37 records · Page 2Linked to original sources

The effects of population structure on the spread of the HIV infection.

A model for the spread of human immunodeficiency virus (HIV) in a population of male homosexuals is presented. The population is divided into five groups on the basis of degree of sexual activity. Within each group, the individuals are classified as 1) susceptible; 2) infective; or 3) removed because of a lack of sexual activity associated with advanced acquired immunodeficiency disease (AIDS). The infective individuals are further subdivided into four stages of infection. Analyses of the model address two questions with regard to the spread of HIV: (1) What is the effect of level of sexual activity on an individual's risk for infection, and (2) What is the effect that assumptions about mixing between groups have on both individual risk and transmission throughout a population? Results from analyses using a number of different parameter estimates show that increased levels of sexual activity increase the likelihood that an individual will become infected. In addition, the initial spread of the disease is markedly affected by variation in the amount of contact among individuals from different subpopulations. The steady-state incidence of the disease is not markedly affected by variation in the contact patterns, but the size of the steady-state population and therefore the proportion of infected individuals in the population does vary significantly with changes in the degree of mixing among subpopulations. These results show clearly the sensitivity of model outcomes to variation in the patterns of contact among individuals and the need for better data on such interactions to aid in understanding and predicting the spread of HIV.

HIV Infections

How accurate is ultrasonography in monitoring IUD placement?

The insertion of two different types of intrauterine devices (Multiload 250 and Silver T) has been monitored in 97 patients through systematic exploration by echography and hysteroscopy. Both techniques seem to be highly reliable in spite of the observation of 9% misplacements of the IUDs not detected by echography. In addition, hysteroscopy enables the diagnosis of frequent associated pathology (endometrial hyperplasia, endometriosis, polyps) difficult to diagnose by echography. The present study demonstrates the fact that the ultrasonography confirmation of IUD localization in the uterus was not always accurate.

Female

Efficacy of intranasal human calcitonin in patients with Paget's disease refractory to salmon calcitonin.

PURPOSE: A cause for the resistance to intranasal salmon calcitonin (sCT) therapy in patients with Paget's disease is the occurrence of neutralizing antibodies to sCT. As a result, a new formulation of intranasal human calcitonin (hCT) was developed, and the efficacy investigated in patients treated earlier with sCT. PATIENTS AND METHODS: Twelve patients with Paget's disease were treated twice daily for 6 months with 1 mg synthetic hCT administered intranasally. Five patients demonstrated low-titer antibodies to sCT, and four of the patients did not respond previously to 1-year therapy with intranasal sCT. The hypocalcemic effect of 3 mg hCT was compared to that of 0.1 mg sCT before and after the intranasal hCT therapy. Serum alkaline phosphatase and the ratio between the urinary excretion of hydroxyproline and creatinine were measured before and during intranasal hCT treatment. RESULTS: The hypocalcemic response to 3 mg intranasal hCT (-6.60 +/- 0.67%, mean +/- standard error) was similar before and at the end of intranasal hCT therapy (-5.92 +/- 0.80%, p greater than 0.1). Intranasal sCT (0.1 mg) lowered serum calcium less effectively (-2.86 +/- 0.76%) than 3 mg intranasal hCT (p less than 0.05). The presence of low-titer antibodies to sCT did not affect the hypocalcemic response to sCT or hCT. As a result of the 6-month intranasal hCT regimen, serum alkaline phosphatase and urinary hydroxyproline/creatinine ratio were reduced to 62 +/- 5% (p less than 0.001) and 80 +/- 7% (p less than 0.05) respectively, of pretreatment levels. In four patients previously resistant to intranasal sCT therapy because of neutralizing antibodies to sCT, serum alkaline phosphatase was similarly lowered by intranasal hCT to 66 +/- 6% of pretreatment levels (p less than 0.05). CONCLUSION: A new formulation of intranasal hCT effectively lowered serum calcium levels, alkaline phosphatase concentrations, and urinary hydroxyproline excretion in patients with Paget's disease, some of whom were previously resistant to intranasal sCT because of neutralizing antibodies.

Administration, Intranasal

Increase in specific antibody-forming cells in human tonsils after oral stimulation with D-53, a ribosomal vaccine.

Thirty subjects who had received an oral ribosomal vaccine to common bacteria of upper respiratory tract infections, and ten controls were tonsillectomized for recurrent infections or rhonchologic pathology. A three-step indirect immunofluorescence technique was used to identify and enumerate specific antibody forming cells (SAFC) in their tonsils. Plasma-cells specific of the four strains being constituents of the oral vaccine (H. influenzae, K. pneumoniae, S. pyogenes and S. pneumoniae) were observed in all samples. The numbers of SAFC were significantly higher in the subjects who had received the oral vaccine. These results support the efficiency or oral immunization in increasing local defenses, even at distance from the sensitized gut-associated lymphoid tissue. These data provide evidence for the homing phenomenon in human mucosae associated lymphoid tissue (MALT).

Adolescent

[Pathology of the yolk sac: endosonographic results].

The yolk sac is the first embryonic structure that is observed by vaginal sonography. It shows up between the fourth and fifth week as regular ring inside the gestational sac. In this study the normal growth of the yolk sac is standardised through the measuring of its diameter, perimeter and area from its appearance till the twelfth week. The aim of this work is to discover the alterations in its size and echographic picture, and to study their repercussions in the foetus.

Abortion, Threatened

Modulation of episodic renin release during sleep in humans.

We previously described a strong concordance between nocturnal oscillations in plasma renin activity and sleep cycles. To examine whether modifying renal renin content or release influences the response to central stimuli linked to sleep stage alternation, plasma renin activity was measured every 10 minutes from 11:00 PM to 8:00 AM in three groups of six subjects. The first group received one 40 mg dose of the diuretic furosemide; the second group underwent the night experiment after 3 days on a low sodium diet; the third group received one 100 mg dose of the beta-blocker atenolol. Each subject underwent a control night when a placebo was given. The nocturnal curves were analyzed with a pulse detection program. For the control nights, 74 of the 83 sleep cycles were associated with significant plasma renin activity oscillations; non-rapid eye movement sleep occurred in the ascending portions and rapid eye movement sleep in the declining portions of the oscillations. These oscillations persisted in the three groups of subjects during the experimental nights and the relation with the sleep stages was not disturbed. Acute stimulation by furosemide amplified the oscillations and led to a general upward trend of the nocturnal profiles. Similarly, a low sodium diet, which led to a slow increase in renal renin content, provoked large oscillations with high initial levels. However, in both cases the mean relative amplitude of the oscillations, expressed as a percentage of the nocturnal means, was similar to that of the control nights and approximated 60%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult

Regulation of serotonin release from enterochromaffin cells of rat cecum mucosa.

The release of endogenous serotonin or previously taken up tritiated serotonin from isolated strips of rat cecum mucosa containing enterochromaffin cells was studied in vitro. Release of tritiated serotonin was increased by potassium depolarization and was decreased by tetrodotoxin, veratridine and the absence of calcium. Endogenous serotonin was released at a lower rate than tritiated serotonin; endogenous serotonin release was stimulated by potassium depolarization but was unaffected by tetrodotoxin, veratridine or the absence of calcium. Carbachol, norepinephrine, clonidine and isoproterenol decreased release of tritiated serotonin but had less or reverse effect on release of endogenous serotonin. The results suggest two different serotoninergic pools within the enterochromaffin cell population.

Animals

Comparison of dietary patterns between population samples in the three French MONICA nutritional surveys.

A nutritional survey was carried out from 1985 to 1987 in three French areas covered by the ischaemic heart disease registers: Bas-Rhin (BR), Haute-Garonne (HG) and the Urban Community of Lille (UCL). 1,128 men aged 45-64 were included in a survey, using the 3-day record method. The results, after adjustment for age, socio-economic status, residence and prescribed diet, showed differences, sometimes significant, between the three samples. Fat represented 37% of the total energy intake in BR, 36% in UCL, and 34% in HG. The P:S ratio ranged from 0.50 in HG, to 0.47 in BR, and 0.40 in UCL. These differences were due to a higher intake of vegetable fat and a lower intake of animal fat in HG. In spite of a very important alcohol intake, with no big differences between the centres (33 to 36 g/day), we noticed that HG drank mainly wine, whereas BR and UCL drank wine and beer in about the same proportions.

Alcoholic Beverages

Blood pressure and dietary intake in a French population sample from three regions.

In order to determine the possible relationship between nutritional factors and blood pressure (BP), a sample of 1128 men of the population living in the three French MONICA centres, Bas-Rhin (BR), Haute-Garonne (HG) and the Urban Community of Lille (UCL), was included in a nutritional survey. Of the sample, 16.2% were taking antihypertensive drugs and 34.1% of the remainder had high BP. Prevalence of high BP was greater in BR and UCL than in HG, the differences persisting after adjustment for body mass index (BMI) and age. BMI and geographic location were the best predictors of high systolic BP (SBP) and diastolic BP (DBP). Age was positively correlated with SBP, but not with DBP. Alcohol intake was the dietary component which had the most consistent relationship with SBP and DBP. However, greater intakes of total fat and of cholesterol were also associated with higher DBP and SBP respectively. A small but significant contribution of sodium chloride to SBP and DBP was also found, whereas no influence of the intake of calcium or of any diary product was observed.

Age Factors

[Which approach should be chosen for inverted nasosinusal papilloma?].

Inverted papillomas are a benign tumors arising from the external wall of the nasal cavity. Sinus extension is easy to evaluate pre-operatively by using the CT-scan. Lateral rhinotomy is therefore not the only way to removing these tumors. Vestibular and endonasal approaches can be considered. Surgical treatment must however remove the tumor tissue completely since recurrence results directly from insufficiency and must be completed by an histological analysis of the whole tissue after its removal in view of its frequent association with carcinoma.

Humans

[Differential diagnosis by MRT of cavernous hemangiomas and malignant tumors of the liver--advantages of the multi-echo technic].

With a retrospective analysis of images from 39 patients with histologically proven liver tumours we tried to determine the best MRT-parameter for detection of cavernous hemangioma (n = 19) and its differentiation from malignoma (metastases n = 17, HCC n = 5). The best differentiation was achieved with the contrast-to-noise ratio between lesion and liver in multi-echo-images with TR/TE = 2,000/210 ms and a definite limit with an accuracy of 84% for hemangioma and 91% for malignoma. The respective intensity ratios (lesion/liver) were 95% and 77%. T2-relation times and the T1- and T2-ratios were also calculated. In contrary to the literature we think that these parameters are not sufficiently discriminating.

Adult

[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

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

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

[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