Search PubMed⌕ Search

Biomedical subjects

J Doucet

Publications and source records attributed to J Doucet.

At least 55 records · Page 3Linked to original sources
PubMed2000

Study of the keratinization process in human hair follicle by X-ray microdiffraction.

Synchrotron X-ray micro-diffraction studies along the follicle and the hair fibre allowed us to follow the keratinization process and the progressive organization of the keratin: i) molecular organization appeared progressively in the follicle; the formation of alpha-helices was completed inside the follicle. ii) supramolecular organization appeared only outside the follicle, far from the bulb; filament structure was observed far from the follicle. Comparisons between structures observed for in vitro and in vivo grown hair, whatever in the bulb or in the fibre, indicate there is no evidence of any structural difference. More, no variation in the transition in vivo/in vitro zone has been observed. In vitro and in vivo fibres exhibited the same structure.

Hair↗
PubMed1999

[Drug use in the elderly. Undesirable drug effects in the elderly: epidemiology and prevention].

A COMMON PROBLEM: Adverse drug effects are common and severe in patients over 70. Most concern widely prescribed drugs or drugs with small safety margins. CLINIC: It is important to recognize the most frequently encountered modes of expression including cardiovascular, metabolic and neuropsychiatric manifestations. The effects of bleeding and low blood sugar are particularly severe. PREVENTION: Certain pharmacological favoring factors are closely related to the aging process. A large number of iatrogenic side effects could however be avoided if the patientís clinical situation is carefully considered in light of the risk of drug interactions, the patientís behavior (observance errors), or prescriber behavior (inappropriate prescriptions in light of the therapeutic goals).

Aged↗
PubMed1999

Percutaneous absorption of sunscreens from liquid crystalline phases.

The purpose of the present study was to investigate the effects of two nonionic surfactants with liquid crystalline structures on the cutaneous availability of two sunscreens. Three liquid crystalline structures were investigated: lamellar, hexagonal and cubic. The diffusion of sunscreens within the liquid crystals was determined by measuring transport kinetics into an unloaded surfactant medium from a similar system loaded with the sunscreens. The diffusion coefficients were the greatest in the cubic systems for benzophenone-4 (a hydrosoluble sunscreen) and in lamellar systems for octyl methoxycinnamate (a liposoluble sunscreen). So the diffusion in this surfactant systems was strongly dependent on the structure of the liquid crystal and on the physicochemical properties of the solute. The transcutaneous fluxes were determined using a Franz-type diffusion cell. The liquid crystalline vehicles modified the transcutaneous fluxes of benzophenone-4 but did not change those of octyl methoxycinnamate. The solute diffusion within the vehicle was not the rate-determining step for transcutaneous permeation for either sunscreen. The diffusion of benzopenone-4 within the stratum corneum and that of octyl methoxycinnamate within the dermis could be the rate-determining steps for their transcutaneous permeation. These two steps could be affected differently by nonionic surfactant vehicles.

Animals↗
PubMed1999

Structural parameters involved in the permeation of propranolol HCl by iontophoresis and enhancers.

The purpose of this work was to study the effect of iontophoretic transport of Propranolol hydrochloride on the lipidic organization of the stratum corneum pretreated under passive or iontophoretic conditions by two model penetration enhancers, sodium lauryl sulfate and hexadecyl trimethylammonium bromide. Characterization of human stratum corneum was performed by X-ray diffraction, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy and differential scanning calorimetry (DSC). The structural properties were compared with the iontophoretic permeability of propranolol hydrochloride on human stratum corneum. The iontophoretic fluxes of propranolol hydrochloride were effectively increased by two-fold in stratum corneum pretreated with sodium lauryl sulfate. In contrast, they were halved in stratum corneum pretreated with hexadecyl trimethylammonium bromide. These results could be related to changes in the electrical and structural properties of the stratum corneum after incorporation of these enhancers.

Adrenergic beta-Antagonists↗
PubMed1999

Side-chains configurations in coiled coils revealed by the 5.15-A meridional reflection on hard alpha-keratin X-ray diffraction patterns.

The origin of the 5.15-A meridional reflection on hard alpha-keratin X-ray diffraction patterns is discussed in terms of side-chains conformations. We show it to reveal specific configurations of the side chains which are common to all two-stranded alpha-helical coiled coils. Combining literature data on crystallised coiled coil pieces and molecular dynamics results with our X-ray diffraction pattern simulations, we propose rules for the attribution of chi1 torsion angles for coiled coils involved in fibres whose structure cannot be resolved at atomic resolution: in a (a b c d e f g) heptad repeat, a and d residues, respectively, adopt mean t and g+ configurations, whereas statistical rules are given for the other residues.

Bacterial Proteins↗
PubMed1999

Modeling alpha-helical coiled coils: analytic relations between parameters.

This paper deals with the alpha-helical coiled coil secondary structure of proteins, which is found not only in many fibrous proteins but also in globular proteins. The standard model used nowadays to describe a coiled coil structure is derived from the mathematical description established more than 40 years ago by F. H. C. Crick (1953, Acta Crystallogr. 6, 685-689) from geometrical arguments. In this paper, we apply stereochemical constraints to the protein chains to refine this model. We present a model based on Crick's calculations with less restrictive hypotheses than the standard model and only requiring a set of initial parameters that can be experimentally measured. In addition, the metrics equation method developed here ensures a minimization of the distortions occurring during the coiling process relating the original straight alpha-helix and the coiled coil minor helix. It leads to a modification of the widely used relation between the numbers of residues per turn in the minor and alpha-helices, mathematically demonstrating a previously semiempirical result. This method can be extended to a wide range of coiled structures.

Models, Molecular↗
PubMed1999

Fecal incontinence in the institutionalized elderly: incidence, risk factors, and prognosis.

PURPOSE: This study was conducted to evaluate the incidence, identify the risk factors, and assess the prognosis of elderly institutionalized patients who develop fecal incontinence. PATIENTS AND METHODS: We enrolled 1,186 patients 60 years of age and older living in long-term care facilities who did not have fecal incontinence. We assessed their medical history, treatment, mobility, and cognitive function. Patients were followed up for 10 months to determine the incidence of fecal incontinence, defined as at least one involuntary loss of feces. Independent risk factors associated with fecal incontinence were identified using Cox proportional hazards models. The prognosis of incontinent patients was assessed by comparing their survival rate with that in the continent patients. RESULTS: Fecal incontinence occurred in 234 patients (20%), and was usually associated with acute diarrhea or fecal impaction. We identified five risk factors for the development of fecal incontinence: a history of urinary incontinence (rate ratio [RR]: 2.0, 95% confidence interval [CI] 1.5 to 2.6); neurological disease (RR: 1.9, 95% CI 1.0 to 3.4); poor mobility (RR: 1.7, 95% CI 1.2 to 2.4); severe cognitive decline (RR: 1.4, 95% CI 1.1 to 1.9); and age older than 70 years (RR: 1.7, 95% CI 1.0 to 2.8). Ten-month mortality in the 89 patients with long-term (> or = 8 days) incontinence was 26%, significantly greater than that observed in the continent group (6.7%) or in the 145 patients with transient incontinence (10%). CONCLUSIONS: Long-lasting or permanent fecal incontinence was associated with increased mortality, suggesting that this symptom is a marker of poor health in older patients. Actions that improve mobility might help prevent fecal incontinence in elderly patients.

Aged↗
PubMed1999

Breast augmentation: compression--a very important factor in preventing capsular contracture.

The incidence of capsular contracture is reduced when smooth-surfaced, saline-filled implants are placed subpectorally, avoiding contamination and the presence of blood. In addition, since the authors began using compression, they have not had one single capsular contracture requiring surgery. The authors' technique, their preoperative and postoperative regimens, an explanation of how they use compression, and the scientific and mathematical explanation of why compression could be the most important factor in preventing capsular compression are described. Of more than 1700 augmentations performed in our private clinic, only 830 could be included in the study. The patients were followed clinically for 1 year, after which time they completed a questionnaire, the results of which showed the authors that capsular contracture had not developed.

Breast Diseases↗
PubMed1998

Organization of microfibrils in keratin fibers studied by X-ray scattering modelling using the paracrystal concept.

Low-angle X-ray scattering patterns of hard alpha-keratin fibers have been studied for more than 50 years but a completely convincing modelling has never been presented. The models which have been proposed so far are specific to the sample and cannot be adapted to others, mainly because they do not use a parametric analytical expression of the distribution function describing the relative positions of the microfibrils. Our new approach is based on a paracrystal distribution function. In addition, a huge background originating from a non-ordered matrix is taken into account. Various hard alpha-keratins from different origins have been studied using our approach. From the rather good modellings obtained, it appears that the diameter of the microfibril is not origin dependent (7.4 nm) whereas the distances between microfibrils and their electron density profiles are. Hair microfibrils can be reasonably approximated by a solid cylinder but a core and an outer ring are necessary for porcupine. Our method is of course not limited to keratin microfibrils; it can be used for modelling equatorial X-ray scattering profiles of all types of hexagonal fibrillar assemblies, which are in fact widely found in biological tissues.

Animals↗
PubMed1998

Nosocomial febrile illness in the elderly: frequency, causes, and risk factors.

BACKGROUND: Although nosocomial febrile illness (NFI) is common in hospitalized patients, it has been less extensively studied in the elderly. OBJECTIVE: To determine the frequency, causes, and risk factors of NFI in elderly inpatients. METHODS: This prospective study involved 608 patients (> or = 65 years of age) admitted in an acute geriatric unit. Investigators followed this cohort until 1 of the following events occurred: development of NFI, discharge from the geriatric unit, or death. The cause of NFI was classified into 3 groups: infectious, noninfectious, and no apparent diagnosis. We systematically studied 17 comorbid conditions, 6 drugs, and 7 invasive procedures. For comparison, the patients were stratified into 2 groups: patients with NFI and patients without NFI. RESULTS: Sixty-six patients (10.9%) with NFI were identified. They were compared with the remaining 542 patients without NFI. In 49 patients (74%) with NFI, the cause was infectious; in 9 (13.5%), it was noninfectious; and in 8 (12.5%), there was no apparent cause. After multivariate analysis, only fecal incontinence (odds ratio [OR], 5.54; 95% confidence interval [CI], 2.13-14.5), congestive heart failure (OR, 2.97; 95% CI, 1.53-5.76), and pressure ulcers (OR, 2.93; 95% CI, 1.19-7.17) were independent risk factors for NFI. The number of invasive procedures preceding the febrile episode was a significant predictor of infection (OR, 3.68; 95% CI, 1.14-9.21). CONCLUSIONS: Nosocomial febrile illness is a common event in elderly hospitalized patients. In 74% of the patients with NFI, an infection is found. Measures to decrease infectious NFI in the elderly require a reduction in the number of invasive procedures.

Aged↗
PubMed1997

A comparison between parallel hairline incisions and perpendicular incisions when performing a face lift.

Our profession has not decided if it is better to incise parallel or perpendicular (at an angle) to hair follicles when performing a brow lift or a face lift. Thirty patients had one side incised parallel and the other side incised perpendicular to hair follicles. Neither the patients nor the examiners knew how each side was incised. By comparing the invisibility, the nonlinearity, the absence of hypopigmentation, and the abundance of hair into and in front of the scar, we obtained statistical proof that if we incised perpendicular to hair follicles (to preserve the deep follicles in the proximal flap), scars were better in 95 percent of patients.

Cell Movement↗
PubMed1997

Anatomy, pathophysiology, and prevention of senile enophthalmia and associated herniated lower eyelid fat pads.

We describe in detail the anatomy and function of the "Lockwood suspensory ligament" and the interrelated function of the orbital contents responsible for the intraorbital position of the eyeball and fat. With age, or because of genetic disposition, the eyeball descends, reducing the space between it and the floor of the orbit. This will inevitably cause forward projection of the extraconical orbital fat, creating herniated fat pads and resulting in enophthalmia. Based on the volume of the bony orbit and its contents, it is likely that relocating, rather then removing, herniated fat pads will greatly improve and prevent the enophthalmia of aging and give the globe a position and a projection of youth. Based on the results of surgery using the capsulopalpebral flap, it is likely that a descended Lockwood suspensory ligament, rather than a weakened orbital septum, is the cause of herniated fat pads and enophthalmia. We feel neither a weakened orbital septum nor an overabundance of orbital fat nor a shallow orbit is responsible for either of these conditions. We give a detailed description of how to raise the globe, preserve and relocate herniated fat pads, and manage and prevent enophthalmia and obtain a beautiful, youthful looking eye.

Adipose Tissue↗