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Biomedical subjects

F Thomas

Publications and source records attributed to F Thomas.

At least 73 records · Page 4Linked to original sources
PubMed1999

Influence of heart rate on mortality in a French population: role of age, gender, and blood pressure.

-The aim of the present study was to assess the effects of high heart rate on mortality in different subgroups in a French population according to age, gender, and blood pressure levels. We studied 19 386 subjects (12 123 men, 7263 women), aged 40 to 69 years, who had a routine health examination at the Centre d'Investigations Préventives et Cliniques (IPC) between 1974 and 1977. Heart rate (HR) measured by ECG was classified into 4 groups: HR1, <60; HR2, 60 to 80; HR3, 81 to 100; and HR4, >100 bpm. Mortality data were recorded for the period of 1974 through 1994. In both sexes, HR was a significant predictor of noncardiovascular mortality. In men, the relative risk (95% confidence interval) for cardiovascular death after adjustment for age and other risk factors in the HR2, HR3, and HR4 groups was 1.35 (1.01 to 1.80), 1.44 (1.04 to 2.00), and 2.18 (1.37 to 3.47), respectively, when compared with HR1. In women, HR did not influence cardiovascular mortality. The association of HR with cardiovascular mortality in men was (1) related to a strong association with coronary but not cerebrovascular mortality, (2) independent of age and hypertension, and (3) influenced by the level of pulse pressure; in patients with high pulse pressure (>65 mm Hg), accelerated HR was not associated with increased cardiovascular mortality. In conclusion, in a large French population, accelerated resting HR represents an independent predictor of noncardiovascular mortality in both genders, and of cardiovascular mortality in men, independent of age and the presence of hypertension. Further investigations are needed to explain the complex interactions between HR, pulse pressure, and cardiovascular complications.

Adult↗
PubMed1999

Genotype-phenotype relationships for the renin-angiotensin-aldosterone system in a normal population.

The renin-angiotensin-aldosterone system plays an important role in blood pressure regulation by influencing salt-water homeostasis and vascular tone. The purpose of the present study was to search for associations of single nucleotide polymorphisms on 3 major candidate genes of this system with the plasma concentrations of the corresponding renin-angiotensin-aldosterone system components considered as quantitative phenotypes. Genotyping was performed in 114 normotensive subjects for different variants of the angiotensinogen (AGT) gene (C-532T, G-6A, M235T), the angiotensin I-converting enzyme (ACE) gene [4656(CT)(2/3)], the aldosterone synthase (CYP11B2), and the type 1 angiotensin II receptor (AT1R) gene (A1166C) by hybridization with allele-specific oligonucleotides (ASO) or enzymatic digestion of polymerase chain reaction products. Plasma levels of AGT, ACE, angiotensin II (Ang II), aldosterone, and immunoreactive active renin were measured according to standard techniques. Platelet binding sites for Ang II were analyzed by the binding of radioiodinated Ang II to purified platelets. B(max) and K(D) values of the Ang II binding sites on platelets of each individual were calculated to examine a possible relationship between these parameters and the AT1R genotype. A highly significant association of the ACE 4656(CT)(2/3) variant with plasma ACE levels was observed (P<0.0001). ANOVA showed a significant effect of the AGT C-532T polymorphism on AGT plasma levels (P=0.017), but no significant effect was detectable with the other AGT polymorphisms tested, such as the G-6A or the M235T. A significant effect association was also found between the C-344T polymorphism of the CYP11B2 gene and plasma aldosterone levels, with the T allele associated with higher levels (P=0.02). No genotype effect of the AT1R A1166C polymorphism was detected either on the B(max) or the K(D) value of the Ang II receptors on platelets.

Adult↗
PubMed1999

Ambulatory and community-based services.

The shift in the site of service delivery from inpatient and institutional to ambulatory and community settings has been prompted by concerns over cost and the prospect for improving the quality of life. In response to these concerns, Medicare has implemented several demonstrations that emphasize ambulatory and community-based services. In this issue, articles are presented on four demonstrations, which focus on the extent to which coordinated care models reduce health care costs, and the cost effectiveness and beneficiary outcomes of disease-specific programs. Two articles are included on home health. One examines home health care in relation to the other Medicare post-acute benefits, and the other focuses on the use of home health care in the treatment of end stage renal disease (ESRD). Finally, two articles report on Section 1915c Medicaid home and community-based waiver programs.

Aged↗
PubMed1998

Diagnosis of bovine brucellosis using a homogeneous fluorescence polarization assay.

To evaluate the fluorescence polarization assay (FPA) for the serological diagnosis of bovine brucellosis, 118 sera from cattle which were culture positive for Brucella abortus, 1751 sera from cattle from premises containing cattle infected with B. abortus, 1222 sera from cattle vaccinated with B. abortus strain 19 and 1199 sera from cattle with no evidence of brucellosis were tested in Argentina, Chile, Mexico and in the American states of Iowa, Missouri and Texas. Initial determination of serological positivity and negativity was based upon reactivity in currently used serological tests, consisting of a rapid screening test, the rose-bengal or the buffered plate antigen tests, followed by a second serological test, the complement fixation test. Sensitivity of the FPA (sera from culture positive animals) ranged from 87.5% to 100%. Serological positivity of cattle from infected premises ranged from 65.5% to 99.0% while the % negative cattle in herds without evidence of brucellosis was between 94.9 and 100%. Of B. abortus strain 19 vaccinated cattle which were positive in at least one in-use serological tests, 88.2% were negative in the FPA. In contrast, previous Canadian studies, sensitivity values were 99.0% and 100% and the specificity in both cases was 100%. This discrepancy was probably due to the use of less well characterized sera in the current study.

Animals↗
PubMed1998

A comparison of sibutramine and dexfenfluramine in the treatment of obesity.

OBJECTIVE: Because long-term weight reduction is often unsuccessful with dietary restriction alone, pharmacological agents have been used to promote weight loss. We have compared the novel (multiple monoamine neurotransmitter reuptake inhibitor) antiobesity drug sibutramine (10 mg once daily) with the extensively studied serotonin-releasing antiobesity agent dexfenfluramine (15 mg twice daily). RESEARCH METHODS AND PROCEDURES: 226 healthy outpatients (aged 18 to 65 years; body mass index > or =27 kg/m2) were included in a 12-week, randomized, double-blind, parallel group study. The main outcome measures were changes in weight, body mass index, waist and hip circumference and ratio, and safety profiles. RESULTS: Mean (+/-SEM) absolute weight loss was 4.5 +/- 0.4 kg in the sibutramine group (n = 112) and 3.2 +/- 0.3 kg in the dexfenfluramine group (n = 112) (endpoint analysis); 4.7 +/- 0.4 kg in the sibutramine group (n = 101); and 3.6 +/- 0.3 kg in the dexfenfluramine group (n = 94) (completers analysis). Comparing the two treatments under the conventional null hypothesis of equality as a secondary analysis, weight loss at endpoint in patients receiving sibutramine was significantly greater than that achieved with dexfenfluramine (p<0.05). Both drugs had similar adverse events profiles: 174 patients (77%) experienced adverse events; 17 patients withdrew due to adverse events (sibutramine, n = 6; dexfenfluramine, n = 11). Pulse rate increased significantly in sibutramine-treated patients (3.6 bpm), but decreased in dexfenfluramine-treated patients (-0.9 bpm). DISCUSSION: Sibutramine (10 mg once daily) is at least as effective as dexfenfluramine (15 mg twice daily) in achieving weight loss in patients with obesity.

Adult↗
PubMed1998

Exploitation of manipulators: 'hitch-hiking' as a parasite transmission strategy.

For many parasites with complex life cycles, manipulation of host behaviour is an adaptation to increase the probability of successful transmission. Since manipulation is likely to be costly, other parasites may exploit hosts already manipulated so as to ensure their transmission without investing in manipulation. Such a cheating strategy, called 'hitch-hiking', could be adaptive in a range of situations. We first propose and discuss criteria that should be met by any parasite to be considered a hitch-hiker. Then, to understand the evolution of the hitch-hiking strategy, we use simple mathematical models to analyse the influence of several variables on the potential benefits for a nonmanipulative parasite of actively seeking a ride to the definitive host with a manipulative parasite. The models suggest that the prevalence or abundance of manipulative parasites will be a key determinant of whether hitch-hiking can be an advantageous option for other parasites. Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1998

[Laparoscopic appendectomy in the adult].

AIM OF THE STUDY: The benefits of laparoscopic appendectomy remain controversial. The aim of the study was to evaluate the advantages and disadvantages of this technique. MATERIAL AND METHODS: Four hundred and forty-eight patients operated on for suspected appendicitis during a 5-year period were analysed in a retrospective study. The preoperative diagnosis was corrected in 21.4% of the cases (8.1% for males and 28.7% for females) and the conversion rate was 9.7%. There were 17 patients with generalized peritonitis and 28 with localized peritonitis. During the past year, this surgical method was introduced in another hospital and a prospective study included 92 consecutive patients operated on for appendicitis. The operating time was 53 minutes and the conversion rate was 7.6%. There were five patients with generalized peritonitis and eight with localized peritonitis. RESULTS: There were no postoperative deaths. In the first period, the morbidity rate was 2.3% in the laparoscopic group without conversion. After pathological examination, there was a 14.2% rate of normal appendix. The mean hospital stay was 4.3 days. In the second period, there were only three minor complications and the mean hospital stay was 4.19 days. CONCLUSION: The choice of laparoscopic approach is associated with some advantages: corrections of the diagnosis (mainly in young women) and simplification of the postoperative course, provided that the surgeon has sufficient experience.

Adolescent↗
PubMed1998

Manipulation of a mollusc by a trophically transmitted parasite: convergent evolution or phylogenetic inheritance?

We investigated the influence of infection by the trematode Curtuteria australis on the burrowing behaviour of its intermediate host, the bivalve Austrovenus stutchburyi. Laboratory experiments and field observations revealed that cockles, unable to bury completely or even partially under the sediment, have a reduced foot length compared with buried individuals. The ability to bury proved to be highly repeatable in field experiments: cockles found at the surface and transplanted to an experimental area did not bury themselves, and cockles found buried stayed buried when relocated. All metacercariae of C. australis were found strictly in the foot and for each of 3 samples collected in different sites, there was a negative and significant relationship between the relative length of the foot and the parasite load. A predation test conducted under natural conditions indicated that cockles with the stunted foot and the altered behaviour are significantly more susceptible to predation by aquatic birds than other cockles. Given that the definitive host of C. australis is an oystercatcher, we first discuss our results in the context of transmission strategy. Comparisons with other studies on more or less related trematode species parasitic in bivalves and evolving under similar constraints for their transmission, shed light on the origin of this adaptation in C. australis.

Animals↗
PubMed1998

Efficacy and tolerability of sibutramine in obese patients: a dose-ranging study.

OBJECTIVES: To assess the weight-reducing effects and tolerability of 5 mg, 10 mg and 15 mg daily doses of sibutramine, a novel serotonin and noradrenaline reuptake inhibitor (SNRI). DESIGN: Multicentre, double-blind, and placebo-controlled study. After a one week run-in period, patients were randomized to receive placebo or sibutramine over a 12-week period. Advice on diet and behaviour modification was provided. One follow-up was conducted four weeks after cessation of treatment. SUBJECTS: 235 obese outpatients, aged 18-65 y with a body mass index (BMI) within the range 27-40 kg/m2. MEASUREMENTS: Weight, height, waist and hip circumference, and medical history, assessment of hunger, satiety, appetite and craving for sweet, savoury and carbohydrate foods, and also for carbohydrate snacking, standard laboratory assessments, blood pressure, heart rate and ECG. RESULTS: The group mean (+/- s.e.m.) weight loss at end-point was 1.4 +/- 0.5 kg for placebo (n = 59), 2.4 +/- 0.5 kg for 5 mg sibutramine (n = 56), 5.1 +/- 0.5 kg for 10 mg sibutramine (n = 59) and 4.9 +/- 0.5 kg (n = 62) for 15 mg sibutramine. The difference observed between the placebo and the 10 mg and 15 mg groups was statistically significant from week 2 onwards (P < 0.01), but there was no significant difference between these sibutramine groups. The percentage of patients losing > 5% of initial bodyweight was significantly greater for 15 mg sibutramine (55%) and 10 mg sibutramine (49%) than for treatment with placebo (19%), (P < 0.001). During the double-blind period, 41 patients (17%) withdrew prematurely and 168 patients (71%) reported 453 adverse events. The incidence and type of adverse event and the rates of withdrawal, were not significantly different in the four groups. No significant differences between the groups were observed, in respect of changes in systolic and diastolic blood pressure, but a significant increase in heart rate (about 4 beats/min) was noted for patients who received 10 mg or 15 mg sibutramine, compared with the placebo (P < 0.001). CONCLUSION: These data demonstrate dose-related weight loss with sibutramine treatment for up to 12 weeks in obese patients. Doses of 10 mg and 15 mg once daily were shown to be similarly effective, well tolerated and significantly more effective than the placebo.

Adult↗
PubMed1998

[Cholesterolemia and total, cardiovascular and cancer mortality. Study of a cohort of 220,000 people].

The distribution of cholesterolemia and their relationship to total mortality, cardiovascular mortality, and cancer mortality were studied in a population of 125,513 men and 96,301 women, aged 16-90. Cholesterolemia in the population increases with age, up to age 50-60 for men and 60-70 for women. Beyond these ages, cholesterolemia decreases very significantly for men and moderately for women. Upon global examination of the entire population, the relationship between cholesterolemia and total mortality is observed as a U-shaped curve. The relationship with cancer mortality is slightly negative in men and appears as a U-shaped curve in women. The relationship with cardiovascular mortality in men is strongly positively correlated when adjusted for body mass index, blood pressure, tobacco consumption, gamma GT, and age. This relationship is not significant in women. There is a significant interaction in the relationship between cholesterolemia and mortality in men for weight, body mass index, vital capacity, maximum expiration volume per second, tobacco consumption, urea, serum albumin, hematocrit, hemoglobin, alkaline phosphatases, gamma GT, red cell volume, and sedimentation rate. Age is a fundamental variable to take into account. Thus, in men under 50 years of age at the time of inclusion, the relationship between cholesterolemia and total mortality shows a positive tendency, and the relationship with cardiovascular mortality is strongly positive. In men over 65 years of age, these relationships are negative. The same tendencies exist for cancer mortality. The reasons for these negative relationships may be related to the decreased cholesterol levels in subjects with malnutrition or diseases (essentially hepatic diseases); this is especially true in older subjects. These data push for additional in-depth analysis of these relationships and interactions, according to age categories and detailed causes of mortality. They also reinforce the idea that, in some patients, low cholesterolemia appears to be a marker for predisposition or the result, but not a cause, of cancer.

Adolescent↗
PubMed1998

Hosts manipulated by one parasite incur additional costs from infection by another parasite.

Manipulation of host phenotype by parasites often serves to increase the predation rate of definitive hosts on intermediate hosts. For intermediate hosts, the indirect consequences of manipulation may extend beyond the direct increase in predation, however. Metacercariae of the trematode Curtuteria australis encyst in the foot of New Zealand cockles, Austrovenus stutchburyi, and stunt its growth, rendering cockles incapable of burrowing into the sediments. Here, we show that cockles manipulated by C. australis are 5 times more likely to be infected by the castrating sporocysts of another trematode than normal, nonmanipulated cockles. Our results indicate that the consequences for C. australis-manipulated cockles are far more important than a simple increase in the risk of predation and that indirect repercussions of manipulation can be as severe as direct ones.

Animals↗
PubMed1998

Nonmanipulative parasites in manipulated hosts: 'hitch-hikers' or simply 'lucky passengers'?

Manipulation of intermediate host behavior to favor parasitic transmission has been demonstrated in a wide of range of parasitic taxa. Recent advances in parasitology have suggested that nonmanipulative parasite species can obtain a high probability of transmission simply by infecting hosts already manipulated ('hitch-hiker' parasites). In this study, from a field collection of Gammarus aequicauda (Amphipoda, second intermediate host), we analyzed the ecological association between the manipulative trematode Microphallus papillorobustus and the 2 nonmanipulative trematodes Microphallus hoffmanni and Levinseniella tridigitata. Although these 2 nonmanipulative parasites should be a priori advantaged when infecting manipulated gammarids, there was no significant ecological association between parasite species. We discuss the possible reasons why these 2 nonmanipulative parasites are only 'lucky passengers' rather than 'hitch-hikers.'

Animals↗
PubMed1997

Use of Doehlert matrices for study of poliovirus-1 adsorption.

Experiments designed according to Doehlert matrices were carried out to study poliovirus-1 adsorption to Na-montmorillonite in a complex aqueous environment. Salt concentration and valence, virus load, clay concentration, and organic matter concentration were included in the design as selected parameters for possible or known involvement in viral adsorption in environmental waters. Use of this experimental design not only allowed to detect and quantify direct influence of the tested parameters upon the viral response, but also to reveal the influence of interactions between these tested factors. Thus, beyond the reassessment of the higher efficiency of multivalent cations on virus adsorption, as opposed to monovalent ones, detection was enabled of a tannic acid/aluminium specific interaction that seemed to be responsible for the nonavailability of these elements for interaction with viruses. Such a statistical tool allows for a gain in experimental accuracy beyond technical improvements and is particularly suited for low-cost study of multifactorial phenomena.

Adsorption↗
PubMed1997

Evaluation of four candidate genes encoding proteins of the dopamine pathway in familial and sporadic Parkinson's disease: evidence for association of a DRD2 allele.

We assessed the role of four candidate genes encoding proteins involved in dopaminergic transmission, the dopamine transporter (DAT), the dopamine receptor D2 (DRD2), and the main catabolic enzymes of dopamine, monoamine oxidase A (MAOA) and B (MAOB), through allelic association studies in a population of familial and sporadic Parkinson's disease (PD). Using intronic polymorphisms of the four candidate genes, we studied the allelic distributions of the polymorphic markers in 18 affected members, one patient was chosen randomly from each PD family; 60 sporadic PD and 60 healthy unrelated control subjects were matched for sex and for country of origin. All subjects were white. To complete the study of the DRD2, we subsequently tested 40 additional sporadic PD and 40 control patients, who were recruited using a similar procedure. For DAT, MAOA, MAOB polymorphisms, similar allelic frequencies were present in familial, sporadic PD and control patients. In contrast, at the DRD2 locus, the overall allelic distribution was significantly different in the sporadic PD (p < 0.01) and in the familial PD groups (p < 0.05), each was compared with the controls. The odd ratios were significant (p < 0.01) in sporadic PD and in familial PD for allele 3 with respective values of 1.84 (95% CI, 1.23-2.74) and 2.83 (95% CI, 1.32-6.08). Individuals who were homozygous for allele 3 were 2.3 times more frequent in the sporadic PD than in controls. Results suggest that DRD2, but not DAT, MAOA and MAOB, might be a genetic determinant of PD in the population tested.

Alleles↗
PubMed1996

A homogeneous fluorescence polarization assay for detection of antibody to Brucella abortus.

A homogeneous fluorescence polarization (FP) assay (FPA) was developed for detection of antibody in bovine sera to Brucella abortus. The assay used O-polysaccharide prepared from B. abortus lipopolysaccharide in the molecular weight range of 20-30 kDa which was conjugated with fluorescein isothiocyanate and used as a tracer. Fluorescence polarization was measured with a FPM-1 fluorescence polarization analyzer. Sample (20 microliters) was added to 2.0 ml of diluent buffer at ambient temperature. A serum blank reading was taken and tracer (10 microliters) to yield approx. 1.5 nM fluorescein equivalents was added. The FP of the tracer was determined after a period of greater than 2 min. A positive reaction was indicated by a significant elevation of the FP reading over the negative control. In a blind study, 9480 bovine sera were tested in addition to sets of four controls which were included with each lot of 100 samples tested. The controls were a strong positive, a weak positive, a negative and a serum derived from a B. abortus strain 19 vaccinated cow. Test sera included 8669 sera from Canadian cattle which were negative by routine serological tests, 561 sera from cows from which B. abortus had been isolated either from tissues or milk and 250 sera from cattle previously vaccinated with B. abortus strain 19 at various times. One lot of O-polysaccharide tracer was used for all tests. The initial cut-off for negative samples in the fluorescence polarization assay was set at 107.2 mP. This resulted in a sensitivity estimate of 98.1 +/- 1.1% and the specificity was 99.8 +/- 0.09%. After decoding the samples and retesting false positive and negative reactions, the sensitivity estimate was 98.5 +/- 1.0% and the specificity was 100%. It became evident that the initial cut-off value was set too high and, using ROC analysis, a cut-off of 90 mP increased the sensitivity to 99.02% while the specificity decreased to 99.96%. Of the 250 sera from vaccinated cattle, 248 were negative giving a point specificity value of 99.2%.

Animals↗