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Biomedical subjects

G Parent

Publications and source records attributed to G Parent.

At least 19 recordsLinked to original sources
PubMed2001

Shaping the reflection near-field optical probe: finite domain time difference modelling and fabrication using a focused ion beam.

An optical fibre ending in a trihedral tip is proposed as a convenient probe for reflection near-field optical microscopy in emission/collection mode. Its shape is obtained by ion milling. A first example of manufacturing and numerical models using the bi-dimensional FDTD method is presented. It confirms the strong influence of the facet angle on the intensity reflected by the probe, which is predicted by a rough analysis. This method can help us to optimize the 'reflection probe' by reducing this offset signal.

Journal Article↗
PubMed2001

Theoretical study of transient phenomena in near-field optics.

A time-domain study of the propagation of a light pulse is made by the finite-difference time-domain method. This method is described briefly and then two applications are presented: creation and diffraction of surface plasmons in the time-domain, and propagation of a light pulse through two tip models, a dielectric one and a metal-coated one. Results on propagation speed of surface plasmons, spatio-temporal shape and spectral study of the field emitted by a tip are presented.

Journal Article↗
PubMed2001

[Parasitological profile of urinary schistosomiasis of the Sourou hydroagricultural complex of Burkina Faso].

In the Sourou area of Burkina Faso, parasitological and malacological surveys of urinary schistosomiasis have been carried out in the constructed sites of Guédougou, Niasan and Débé dating respectively from 1967, 1986 and 1996. The investigations covered also the traditional villages of Lanfiera, Di, Poro, Tiao and Mara situated in the middle of the hydroagricultural planning for the first, very close to the lake for the second and about twenty kilometres distant for the three last. These towns represent the main sites in the Sourou area. The results of the parasitological surveys showed that urinary schistosomiasis was present in all sites. The levels of prevalence varied considerably: 70.3% in Guiédougou, 40.8% in Niassan, 8.5% in Débè in the irrigated zone, 55.6% in Lanfiéra, 56.8% in Di, 13.2% in Poro, 83.3% in Tiao and 64.7% in Mara. Concerning the malacological investigation, two species (Bulinus senegalensis and B. truncatus) were shown to be intermediate hosts of Schistosoma haematobium. The first was endemic to the area while the second was compatible with S. haematobium from the Sourou and other zones. Compared to the results of earlier investigations, the endemic had worsened with differences according to sites. This disparity of prevalence levels which has already been observed in other hydroagricultural area results from many factors, among which the impact of irrigation activities, the aquatic biotope system (irrigation canals, natural lake, pools and temporary rivers) and the type of contact of human communities with water rank high. Schistosomiasis expansion is amplified by the intermediate host dynamics and the introduction of new schistosomes carried by the new workers arriving from all over the country. In these conditions, in order to reduce rapidly prevalence levels, preventive measures should be centred on chemotherapy for the population. The treatment should be administered during a period of weak intermediate host density and be directed towards in-coming workers. Such an approach should be able to check the spread of schistosomiasis naturally occurring with the irrigation of new sites.

Adolescent↗
PubMed1999

[Schistosomiasis in the region of Ziga (Burkina Faso) before the construction of a dam].

The authors report the results of a survey on schistosomiasis in the zone of Ziga (Burkina Faso) where a dam is going to be built. They examined 438 children aged from 7 to 15 years in 5 villages. The appraisal of macroscopic or microscopic hematuria, urine filtration, stool analysis and ultrasonographic examination made possible the assessment of the prevalence and severity of both schistosomiasis. The area was hyperendemic for urinary schistosomiasis. The general prevalence of S. haematobium was higher than 46% and 55% of the children presented at least one lesion of the bladder and 2% of hydronephrosis at ultrasonography. Intestinal schistosomiasis was not observed although few cases have been described in the regional hospital and intermediate host snails have been collected in the area. A surveillance of schistosomiasis, based on school surveys, was strongly recommended in the dam area.

Adolescent↗
PubMed1998

Immune recovery of malnourished children takes longer than nutritional recovery: implications for treatment and discharge.

Protein-energy malnutrition decreases cellular immunity yet immune recovery has rarely been investigated during nutritional rehabilitation. Malnourished children from low income families of Cochabamba (Bolivia) were hospitalized for 2 months in the Center for Immune and Nutritional Rehabilitation (CRIN), of the German Urquidi Materno-Infantil Hospital. They received a special four-step diet. Nutritional status was determined by a daily clinical examination and weekly anthropometric measurements. Immune status was assessed by weekly ultrasonography of the thymus. The classical criterion for discharge (90 per cent of median reference weight for height) was reached after the first month, whereas a 2-month period was required for complete immunologic recovery. The children belonged to disadvantaged population groups with high exposure to disease. In such an environment, discharge based only on nutritional status after 1 month of treatment could explain frequent relapses because the children were still immunodepressed.

Anthropometry↗
PubMed1996

Quantitative comparison of casein and rapeseed proteolysis by pancreatin.

The problem of quantitative comparison of kinetic curves was solved for casein and rapeseed pancreatin hydrolysis in a membrane reactor, which ensured the measurement of proteolysis kinetics for the products with a molecular weight of less than 1000. Coordinates were derived which provided good linearization of kinetic curves and the determination of relative rate constants irrespective of reagent concentrations, E0/S0 ratio and time intervals of kinetic measurements. When the relative rate constants of the release of the individual amino acid residues in the low-weight proteolysis products were compared, trypsin-dependent constants (for Lys and Arg residues) were found to be two times less for rapeseed than for casein, and chymotrypsin-dependent constants (for Tyr and Phe residues) were approximately 1.3 times higher for rapeseed than for casein. Statistical analysis demonstrated that the distribution of constants was narrower for rapeseed than for casein. Differences between target (Arg, Lys, Tyr and Phe) and non-target constants of release in the form of peptides and free amino acids, or in the form of free amino acids only, were attributed on the differences in the peptide bond masking for casein and rapeseed proteins. Computer simulation of proteolysis kinetics was performed by PROTEOLYSIS program package to confirm the dependence of rate constant distribution on the state of masking.

Amino Acids↗
PubMed1996

[Training needs for educators and nurses using the individualized services plan in mental health].

With the help of the method elaborated by Herskowitz (1977), this study examines the training needs of 42 workers (19 educators and 23 nurses) using when needed, the individualized services plan in a context of external services (deinstitutionalization) in mental health and internal services (hospital). A modified version of a questionnaire developed by Hurteau (1988) adapted to the context of mental health, identifies the training needs of workers using the individualized services plan under five specific dimensions and three types of knowledge. In the light of results obtained, certain training needs appear as top priority, especially conducting meetings and methods of elaboration of individualized services plan. Moreover, workers would like to obtain training on community-oriented services offered to people with needs in mental health.

Community Mental Health Services↗
PubMed1994

In vitro lymphocyte-differentiating effects of thymulin (Zn-FTS) on lymphocyte subpopulations of severely malnourished children.

This work investigates how thymic dysfunction contributes to the depression of cell-mediated immunity in protein-energy malnutrition (PEM). In Bolivian children hospitalized for severe PEM, the size of the thymus was measured by echography, and the lymphocyte subpopulations were detected by using monoclonal antibodies. These data were compared with those obtained from healthy control subjects. Regardless of the clinical form of PEM, our results show a high degree of T lymphocyte immaturity in severely malnourished children, which correlates with a severe involution of the thymus. Before in vitro incubation with thymulin, this significant increase in the percentage of circulating immature T lymphocytes was concomitant with a decrease in mature T lymphocytes and a slight increase in cytotoxic T subpopulations. After in vitro incubation with thymulin, immature T lymphocytes decreased and mature T lymphocytes increased.

Anthropometry↗
PubMed1991

Metabolic and contractile responses of rat fast-twitch muscle to 10-Hz stimulation.

Contractile and metabolic responses of rat fast-twitch gastrocnemius-plantaris muscles were studied. Acute in situ 10-Hz stimulation (STIM) for two 60-min periods, separated by 60 min of recovery (REC), was used. Muscles were removed at 1, 3, 15, 60, 75, 120, 123, or 180 min for metabolite measurements. Twitch and tetanic tensions were reduced to 36 and 28% of initial during the first 60 min of STIM. During REC, these tensions returned only to 56-58% of initial by 120 min. These contractile responses did not parallel changes in metabolites in mixed muscle. pH was reduced from 7.0 to 6.4 by 1 min, but by 15 min of STIM had returned to resting levels. Free ADP and AMP increased 3- and 15-fold during STIM, then decreased to resting levels by 3 min of REC. The most sensitive indicator of metabolic stress during STIM and REC was the phosphorylation potential, which varied up to 40-fold. After initial phases of depletion, ATP and phosphocreatine levels were partially restored despite ongoing STIM. Approximately 75% of the change in ATP level could be accounted for by IMP. In red gastrocnemius [fast-twitch red (FTR)] muscle, IMP was increased by 3 min of STIM but returned to control values by 60 min. Thus reamination of IMP occurred during contractions of FTR muscle. Metabolic and contractile responses during the second STIM period (120-180 min) were similar to the first. This cycle of metabolic and contractile responses occurs in fast-twitch muscle which, with chronically repeated STIM and REC periods, undergoes large phenotypic changes as a result of use.

Adenine Nucleotides↗
PubMed1989

In vitro amino acid digestibility of food proteins as measured by the digestion cell technique.

The digestibility of proteins and individual amino acids of nineteen selected foods was determined by an in vitro assay. Samples were hydrolysed with pepsin for 30 minutes in an acidic medium; the pH was then raised to 7.5 and the mixture poured into the dialysis bag (molecular weight cut-off 1000) of a digestion cell with pancreatin. Digestion products, mixtures of free amino acids and low molecular weight peptides which pass through the dialysis membrane, were collected for 6 hours by sodium phosphate buffer circulation. All proteins from animal sources displayed a digestibility similar to casein, except for breakfast sausage. Vegetable proteins showed intermediate digestibility, except for cereals (lower) or peanut butter (higher). Target amino acids of enzymes were generally more readily hydrolysed. However, compared to other animal proteins, glycine in milk products, valine, isoleucine, methionine and lysine in breakfast sausage and hot dog, and histidine in tuna were more easily released. Overheating of non-fat dried milk not only reduced the lysine digestibility, but also that of methionine, phenylalanine, histidine and cystine. Among vegetable proteins, wheat products were characterized by a relatively greater release of threonine, isoleucine and histidine, and peas by a lower digestibility of methionine and lysine. Proline of soy isolate and isoleucine of pinto bean were resistant to hydrolysis while arginine of pinto beans and of rice-wheat-gluten was easily released.

Amino Acids, Essential↗
PubMed1988

Thymulin (Zn-FTS) activity in protein-energy malnutrition: new evidence for interaction between malnutrition and infection on thymic function.

The combined effects of protein-energy malnutrition (PEM) and infection on thymic function evaluated by specific plasma thymulin activity were studied in Senegalese children: 29 hospitalized in Dakar for severe malnutrition and various diseases; 9 infected without sign of severe PEM, living in Dakar; 13 apparently healthy, uninfected, living in Dakar; and 7 apparently healthy, uninfected, living in Paris. Most of the free-living children in Dakar suffered from mild to moderate PEM. The specific thymulin activity (total plasma activity minus the activity recorded after adsorption of the plasma with a monoclonal antithymulin antibody) was almost undetectable in the infected children and was normal only in the children living in Paris. Such activity might be decreased by moderate and severe PEM and severe malnutrition may not be the only underlying cause of depressed level of thymulin in malnourished children from the Third World. Concurrent infections are important factors.

Blood Proteins↗
PubMed1988

Thymulin (facteur thymique serique) and zinc contents of the thymus glands of malnourished children.

Protein-energy malnutrition (PEM) leads to an immune deficiency, which is now well documented. Some investigators have suggested that the associated zinc deficiency is important in thymic involution and changes in cellular immunity. To evaluate the respective roles of nutritional deficiency, infection, and zinc in the alteration of thymic function, we measured the amounts of thymulin (facteur thymic serique, or FTS) and of Zn in the thymus glands of 58 Senegalese children who died in various stages of malnutrition. In the severe forms (marasmus, kwashiorkor, and marasmic kwashiorkor) the thymus was tiny and contained very little thymulin. The Zn content of the thymus was high whatever the nutritional state of the subject and was related significantly only to the presence of infections. In Senegalese children thymic atrophy and depleted thymulin content are associated with severe PEM but not systemic infection or depleted thymic Zn content.

Animals↗
PubMed1987

Effect of dietary proteins on time-dependent changes in plasma amino acid levels and on liver protein synthesis in rats.

The effects of four dietary proteins on plasma amino acid (PAA) levels in portal vein and aorta and on hepatic ribosome aggregation were investigated in rats fed 10% protein diets ad libitum. Proteins studied were beef, casein, rapeseed and soybean. Measurements were made at 2000, 2300, 0200, 0500 and 0800 h. Portoaortic differences in essential amino acids (EAA) in plasma were calculated and compared to dietary EAA to verify the time-dependent changes in their intestinal absorption. Each protein generated different variations in portal and aortic PAA levels. Rapeseed produced the lowest plasma concentrations of EAA, but its portoaortic differences were as large as those of the other proteins. With each protein, proportions of EAA in plasma (in contrast to concentrations) tended to remain constant in portal vein and aorta over the 12-h period. Significant correlations between portoaortic differences and dietary EAA were found in all groups, but at varying times, indicating that the kinetics of intestinal absorption were dependent on the protein fed. So were variations in liver polysome distribution. For rapeseed and soybean, times of most active protein synthesis were 0200 and 0500 h; with beef and casein, variations between sampling times were not significant. No direct relationship was found between magnitude and composition of PAA portoaortic differences and ribosome aggregation. Thus these two parameters were both affected by dietary proteins, but no synchrony was evidenced between them.

Amino Acids, Essential↗
PubMed1987

[Malaria, anemia and nutritional status: longitudinal study of their interaction in a sahelian zone (Senegal)].

Two villages in the sahelian zone of the Senegal river Basin, were surveyed during one year. On 5 occasions (May, July, October 1982, January, March 1983) 200 persons were clinically examined and a parasitological (parasite rate and specific antibodies), haematological and biochemical examination was done. At the same time an entomological survey was performed. The two vectors were Anopheles gambiae ss. and A. arabiensis with a predominance of the first. Although the number of infective bites is low, the transmission risk is high, at least one a year. The parasite rate is low (15%) with almost no seasonal variation although transmission occurs only during 3-4 months. Correspondingly low titres of malaria antibodies are present. The nutritional status of the population is on the limit of normal. It was not possible to make significant correlations between malaria and the nutritional status except for anaemia where evolution seems to be more related to malaria than to nutrition.

Adolescent↗
PubMed1986

Levels of antibodies to Plasmodium falciparum sporozoite surface antigens reflect malaria transmission rates and are persistent in the absence of reinfection.

Antibodies reacting with Plasmodium falciparum sporozoite surface antigens were measured by an immunofluorescence assay using wet preparations of sporozoites attached to poly-L-lysine-treated glass slides, a procedure which was found to be more specific than one using glutaraldehyde-treated and dried preparations. Subjects recovering from a first attack were found to be negative. In two African villages which differed in the level at which mosquitoes transmit the disease (1 and 100 infective bites per year and per individual), both the prevalence by age group and the levels of anti-sporozoite antibodies differed markedly, as follows. In the low-transmission area, these antibodies were not detected in subjects aged 2 to 10 years; thereafter, prevalence increased gradually with the age of the subject and reached 90% in subjects aged 50 to 80 years. In the high-transmission area, all of the subjects studied, including the younger ones, were positive. Anti-sporozoite antibody levels were independent of the levels of antibodies directed against blood stages. On average, the mean antibody titers were equal to 1/16 in the first village and 1/1,650 in the second one. These results suggest that stage-specific antibodies reflect the cumulative number of sporozoites inoculated in humans by mosquitoes and may therefore have useful epidemiological applications. In addition, the presence of stage-specific antibodies in the sera of African adults collected at different times after departure from the endemic area indicates that they may last for several years. During the course of this study, we observed a heterogeneity of immunofluorescence labeling in parasite populations prepared from mosquito salivary glands. This raises the question of possible qualitative or quantitative antigenic differences or both between one sporozoite and the other.

Adolescent↗
PubMed1985

The role of nutrition in primary health care. Practical considerations for the vaccination programme in Kaya, Burkina Faso.

A programme of intervention in problems of nutrition is presented as part of a vaccination programme such as the one carried out in Kaya, Burkina Faso. In this region the most widespread type of malnutrition is essentially 'energy-malnutrition' more than 'protein-malnutrition'; other more specific deficiencies are observed: it concerns iron, folates and vitamin A. As a consequence the first aim of intervention is to eradicate the protein-energy-malnutrition. To achieve this a specialized health worker will have to trace first the undernourished children (either by measuring their arm circumference of with the aid of a thinness diagram). The he/she will propose a programme of nutritional rehabilitation using locally available products, which will be completed with a demonstration of oral rehydration. The promotion of adequate nutrition and of vaccination against major infectious diseases are two of the indispensable activities as parts of primary health care. Starting from the nutritional situation prevailing in Burkina Faso we propose concrete interventions which will be applied among others in the vaccination programme in Kaya province.

Burkina Faso↗