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Biomedical subjects

L Kam

Publications and source records attributed to L Kam.

At least 19 recordsLinked to original sources
PubMed2006

[Factors for non-observance of the extended program timetable for vaccination in health districts: the case of Boussé in Burkina Faso].

UNLABELLED: Prevention through vaccination is a strong means to fight pediatric lethal diseases. In Burkina Faso, one of the main problems for vaccination is the non-respect of the vaccination timetable bringing about a significant reduction of validity of administered doses. OBJECTIVES: The authors had for aim to assess reasons for the non-compliance to the timetable. A transversal study was carried out in the Boussé health district to: 1) analyze the qualitative and organizational factors of the vaccination services linked to this non compliance; 2) analyze community factors accounting for this situation. POPULATION AND METHOD: The study target group included mothers of children aged 0 to 11 months vaccinated by the vaccination team of the Boussé health district from August 1st, 2003 to June 30th, 2004, and the vaccination team. Variables covered in this study included sociodemographic factors, the organization of vaccination campaigns, the mothers' perception of health service organization, the vaccination team's experience, vaccinal safety, knowledge of vaccination timetable. RESULTS: The following were identified as key factors for the non-observance of the vaccination timetable: poor organization of the vaccination services, inadequate competence of the vaccination team, poor educational level of mothers, poor communication level with mothers, postvaccination side effects. CONCLUSION: The study recommends the following: training of vaccination providers, a better organization of vaccination services, and the implementation of a communication plan.

Adult↗
PubMed2006

[W135 meningococcus meningitis: study of 148 cases observed in 2002 and 2003 at the National Teaching Hospital of Ouagadougou, Burkina Faso].

The purpose of this report is to describe the bacteriological features, clinical signs and therapeutic outcome of 148 cases of W135 meningococcus meningitis observed during meningitis outbreaks in Burkina Faso in 2002 and 2003. Diagnosis was based on microbiological study of cerebrospinal fluid. Cases of meningococcus meningitis were recorded throughout the study period with the peak number of cases occurring around the 14th week. There was a slight male predominance (56.1%) and young patients between one and 15 years accounted for 81.7% of cases. The mean interval between onset of symptoms and hospitalization was 2.6 days and the mean duration of hospitalization was 5.5 days. The most common clinical signs were fever (98.6%), stiff neck (90.5%),Brudzinski's sign (85.1%),Kernig's sign (66.2%), altered consciousness (41.9%), vomiting (36.5%) and headaches (34.5%). In most cases treatment with a singie dose of chiorazuphenicol in oil was curative. Overall mortality was 15.5% idth no correlation with sex or age. Seventeen of the 23 deaths occurred within 24 hours after their admission to the hospital. The other six deaths occurred on the second day after admission inS cases and fifth day in one case. Convulsions, shock and altered consciousness were consistent poor prognostic signs. A correlation was found between mortality and interval for hospitalization with better survival in patients receiving prompt treatment. Study of the susceptibility of 102 samples showed that W135 meningococcus was sensitive to penicillin G, ampicillin,ceftriaxone and chloramphenicol but resistant to sulfamides (cotrimoxazole). Bacterial meningitis is an Important factor of morbidity and mortality worldwide. Our findings indicate that the bacteriological, clinical and epidemiological characteristics of W135 meningococcus is do not differ greatly from those of meningococcus A. Since W135 meningitis is susceptible to antibiotics used to cure meningitis, campaigns to promote early detection and treatment must be continued.

Adolescent↗
PubMed2002

Selective adhesion of astrocytes to surfaces modified with immobilized peptides.

Under serum-free conditions, rat skin fibroblasts, but not cortical astrocytes, selectively adhered to glass surfaces modified with the integrin-ligand peptide RGDS. In contrast, astrocytes, but not fibroblasts, exhibited enhanced adhesion onto substrates modified with KHIFSDDSSE, a peptide that mimics a homophilic binding domain of neural cell adhesion molecule (NCAM). Astrocyte and fibroblast adhesion onto substrates modified with the integrin ligands IKVAV and YIGSR as well as the control peptides RDGS and SEDSDKFISH were similar to that observed on aminophase glass (reference substrate). This study is the first to demonstrate the use of immobilized KHIFSDDSSE in selectively modulating astrocyte and fibroblast adhesion on material surfaces, potentially leading to materials that promote specific functions of cells involved in the response(s) of central nervous system tissues to injury. This information could be incorporated into novel biomaterials designed to improve the long-term performance of the next generation of neural prostheses.

Amino Acid Sequence↗
PubMed2001

High refractive index substrates for fluorescence microscopy of biological interfaces with high z contrast.

Total internal reflection fluorescence microscopy is widely used to confine the excitation of a complex fluorescent sample very close to the material on which it is supported. By working with high refractive index solid supports, it is possible to confine even further the evanescent field, and by varying the angle of incidence, to obtain quantitative information on the distance of the fluorescent object from the surface. We report the fabrication of hybrid surfaces consisting of nm layers of SiO(2) on lithium niobate (LiNbO(3), n = 2.3). Supported lipid bilayer membranes can be assembled and patterned on these hybrid surfaces as on conventional glass. By varying the angle of incidence of the excitation light, we are able to obtain fluorescent contrast between 40-nm fluorescent beads tethered to a supported bilayer and fluorescently labeled protein printed on the surface, which differ in vertical position by only tens of nm. Preliminary experiments that test theoretical models for the fluorescence-collection factor near a high refractive index surface are presented, and this factor is incorporated into a semiquantitative model used to predict the contrast of the 40-nm bead/protein system. These results demonstrate that it should be possible to profile the vertical location of fluorophores on the nm distance scale in real time, opening the possibility of many experiments at the interface between supported membranes and living cells. Improvements in materials and optical techniques are outlined.

Contrast Sensitivity↗
PubMed2001

Cell adhesion to protein-micropatterned-supported lipid bilayer membranes.

A new method for constructing controlled interfaces between cells and synthetic supported lipid bilayer membranes is reported. Microcontact printing is used to define squares and grid lines of fibronectin onto glass, which subsequently direct the self-assembly of fluid lipid bilayers onto the complementary, uncoated regions of the surface. Features of fibronectin as small as 5 microm effectively control the lateral organization of the lipid bilayers. These fibronectin barriers also facilitate the adhesion of endothelial cells, which exhibit minimal adhesion to fluid supported lipid bilayers alone. Cells selectively adhere to the features of fibronectin, spanning over and exposing the cells to the intervening regions of supported lipid bilayer. Cell spreading is correlated with both the geometry and dimensions of the fibronectin barriers. Importantly, lipids underlying adherent cells are laterally mobile, suggesting that, in contrast to the regions of fibronectin, cells were not in direct contact with the supported membrane. Protein micropatterning thus provides a valuable tool for controlling supported membranes and for juxtaposing anchorage-dependent cells with lipid bilayers. These systems should be generally useful for studying specific interactions between cells and biomolecules incorporated into supported membranes, and as an approach for integrating living cells with synthetic, laterally complex surfaces.

Animals↗
PubMed2001

Retinal pigment epithelial cell adhesion on novel micropatterned surfaces fabricated from synthetic biodegradable polymers.

Novel synthetic biodegradable polymer substrates with specific chemical micropatterns were fabricated from poly(DL-lactic-coglycolic acid) (PLGA) and diblock copolymers of poly(ethylene glycol) and poly(DL-lactic acid) (PEG/PLA). Thin films of PLGA and PEG/PLA supported and inhibited, respectively, retinal pigment epithelial (RPE) cell proliferation, with a corresponding cell density of 352,900 and 850 cells/cm2 after 7 days (from an initial seeding density of 15,000 cells/cm2). A microcontact printing technique was used to define arrays of circular (diameter of 50 microm) PLGA domains surrounded and separated by regions (width of 50 microm) of PEG/PLA. Reversed patterns composed of PEG/PLA circular domains surrounded by PLGA regions were also fabricated. Both micropatterned surfaces were shown to affect initial RPE cell attachment, limit cell spreading, and promote the characteristic cuboidal cell morphology during the 8-h period of the experiments. In contrast, RPE cells on plain PLGA (control films) were elongated and appeared fibroblast-like. The reversed patterns had continuous PLGA regions that allowed cell-cell interactions and thus higher cell adhesion. These results demonstrate the feasibility of fabricating micropatterned synthetic biodegradable polymer surfaces to control RPE cell morphology.

Biodegradation, Environmental↗
PubMed2001

Axonal outgrowth of hippocampal neurons on micro-scale networks of polylysine-conjugated laminin.

Microcontact printing was used to define an interconnected lattice network of polylysine-conjugated laminin, a protein-polypeptide ligate that is an effective promoter of neuron outgrowth on material surfaces. In the presence of serum proteins, rat hippocampal neurons selectively adhered to features of polylysine-conjugated laminin as narrow as 2.6 microm in width. Adhering neurons extended long axonal processes, which precisely followed and did not deviate from the prescribed patterns, demonstrating that neurons respond to this protein with high selectivity and that these techniques effectively provide long-range guidance of axonal outgrowth. Further examination of neuron response under serum-free cell culture conditions demonstrated that the outgrowth-promoting activity of polylysine-conjugated laminin was attributed to biologically active laminin. Together, these results demonstrate that polylysine-conjugated laminin provides for high-precision guidance of neuron attachment and axon outgrowth on material surfaces in a serum-independent manner. This ability to guide hippocampal neuron response in low-density, serum-free culture with high precision is valuable for the development of advanced, neuron-based devices.

Animals↗
PubMed2000

Attachment of astroglial cells to microfabricated pillar arrays of different geometries.

We studied the attachment of astroglial cells on smooth silicon and arrays of silicon pillars and wells with various widths and separations. Standard semiconductor industry photolithographic techniques were used to fabricate pillar arrays and wells in single-crystal silicon. The resulting pillars varied in width from 0. 5 to 2.0 micrometer, had interpillar gaps of 1.0-5.0 micrometer, and were 1.0 micrometer in height. Arrays also contained 1.0-micromter-deep wells that were 0.5 micrometer in diameter and separated by 0.5-2.0 micrometer. Fluorescence, reflectance, and confocal light microscopies as well as scanning electron microscopy were used to quantify cell attachment, describe cell morphologies, and study the distribution of cytoskeletal proteins actin and vinculin on surfaces with pillars, wells, and smooth silicon. Seventy percent of LRM55 astroglial cells displayed a preference for pillars over smooth silicon, whereas only 40% preferred the wells to the smooth surfaces. Analysis of variance statistics performed on the data sets yielded values of p > approximately.5 for the comparison between pillar data sets and < approximately.0003 in the comparison between pillar and well data sets. Actin and vinculin distributions were highly polarized in cells found on pillar arrays. Scanning electron microscopy clearly demonstrated that cells made contact with the tops of the pillars and did not reach down into the spaces between pillars even when the interpillar gap was 5.0 microm. These experiments support the use of surface topography to direct the attachment, growth, and morphology of cells. These surfaces can be used to study fundamental cell properties such as cell attachment, proliferation, and gene expression. Such topography might also be used to modify implantable medical devices such as neural implants and lead to future developments in tissue engineering.

Actins↗
PubMed2000

Aligned microcontact printing of micrometer-scale poly-L-lysine structures for controlled growth of cultured neurons on planar microelectrode arrays.

We describe a method for producing high-resolution chemical patterns on surfaces to control the attachment and growth of cultured neurons. Microcontact printing has been extended to allow the printing of micron-scale protein lines aligned to an underlying pattern of planar microelectrodes. Poly-L-lysine (PL) lines have been printed on the electrode array for electrical studies on cultured neural networks. Rat hippocampal neurons showed a high degree of attachment selectivity to the PL and produced neurites that faithfully grew onto the electrode recording sites.

Animals↗
PubMed1999

Crohn's disease-associated genetic marker is seen in medically unresponsive ulcerative colitis patients and may be associated with pouch-specific complications.

PURPOSE: Genetic markers have been used to define subgroups of patients within the broad categories of Crohn's disease and ulcerative colitis that may differ in clinical course and response to medical therapy. The tumor necrosis factor microsatellite haplotype a2blc2d4e1 has been found previously to be present in 24 percent of patients with Crohn's disease and only 5 percent of patients with ulcerative colitis. This study examined associations between this microsatellite haplotype and the postoperative clinical course of patients with ulcerative colitis undergoing ileal pouch-anal anastomosis. METHODS: As part of a large, controlled, prospective study to correlate genetic markers with clinical phenotypes, tumor necrosis factor microsatellite alleles at five loci (a, b, c, d, and e) were determined from genomic DNA by polymerase chain reaction in 32 patients with a clinical and histopathologic diagnosis of ulcerative colitis who underwent ileal pouch-anal anastomosis for medically unresponsive disease. All patients with ileal pouch-anal anastomosis were also studied prospectively for pouch-specific complications. RESULTS: The tumor necrosis factor haplotype a2blc2d4e1 was present in 11 patients. Median follow-up was 19 months. Thirteen patients had a pouch-specific complication (12 pouchitis and 1 pouch-perineal fistula). Six of 11 patients (55 percent) with the haplotype had a pouch-specific complication compared with 7 of the 21 patients (33 percent) who did not possess this haplotype (P = 0.22). Median time from surgery to pouch-specific complication was eight months. Patients with the haplotype had a median time to pouch-specific complication of three months, whereas patients without the haplotype had a median time of 11 months (P = 0.04). In addition, 36 percent of patients with the haplotype had chronic pouch complications vs. only 10 percent of patients without the haplotype (P = 0.05). CONCLUSION: The Crohn's disease-associated tumor necrosis factor haplotype a2blc2d4e1 may define a subgroup of medically unresponsive patients with ulcerative colitis who are predisposed to a higher incidence of pouch-specific complications after ileal pouch-anal anastomosis.

Adult↗
PubMed1999

Functional and ethnic association of allele 2 of the interleukin-1 receptor antagonist gene in ulcerative colitis.

BACKGROUND & AIMS: The role of the interleukin (IL)-1 receptor antagonist (IL-1ra) in predisposing an individual to inflammatory bowel disease (IBD) is controversial. This study aimed to determine the association between intron 2 IL-1ra polymorphism and IBD by performing a multiethnic case-control study and to assess its functional significance. METHODS: A total of 236 patients with ulcerative colitis (UC), 196 patients with Crohn's disease (CD), and 338 ethnically matched control patients treated at LAC-USC and Cedars-Sinai Medical Centers and the University of Milan Medical Center were genotyped for a variable length polymorphism in intron 2 of the IL-1ra gene (IL-1RN). Total IL-1ra protein production rates in peripheral blood mononuclear cells (PBMCs) were correlated with carriage of allele 2 of the IL-1RN gene (IL-1RN*2). RESULTS: In the LAC-USC group, UC patients (n = 60) had an increased frequency of at least 1 copy of IL-1RN*2 compared with controls (n = 129) (70% vs. 33%; P < 0.01; odds ratio [OR], 4.7). The frequency of IL-1RN*2 carriage in the Cedars-Sinai group was 59% in UC, 45% in CD, and 42% in controls (P < 0.01; OR, 2.0). A significant difference was observed only in the Jewish subgroup (P = 0.003; OR, 5.0). The association was not detected in UC or CD patients treated at the University of Milan. The ORs of 4.7 and 5.0 appear to be the highest reported in any UC population for any genetic markers. Further, carriage of IL-1RN*2 was associated with decreased production of total IL-1ra protein in cultured PBMCs from both UC patients and controls. CONCLUSIONS: These results provide further evidence that IL-1ra is important in the predisposition to UC, there may be genetic or pathogenetic heterogeneity between different ethnic groups, and UC and CD are genetically distinct diseases.

Adolescent↗
PubMed1999

Correlation of astroglial cell function on micro-patterned surfaces with specific geometric parameters.

Microcontact printing techniques were used to modify silicon substrates with arrays of hexagonal features of N1[3-(trimethoxysilyl) propyl]diethylenetriamine (DETA) surrounded by octadecyltrichlorosilane (OTS), which are hydrophilic, cell-adhesive and hydrophobic, non-adhesive organosilanes, respectively. In the presence of serum proteins, LRM55 cell adhesion and morphology on these modified surfaces were best correlated to the width of the cell-adhesive features. On surfaces modified with small (5 microm in width) cell-adhesive features, LRM55 cells elaborated only thin processes. As feature width was increased, cells on these surfaces exhibited increased cell spreading and elaborated wide processes. On surfaces modified with large (>35 microm in width) features, single cells adhered to and spread upon individual DETA features. In a similar fashion, LRM55 cell adhesion density increased with increasing feature width; this correlation could be represented by a simple, second-order relation, and was independent of all other measures of pattern geometry. The results of this study provide evidence that micro-patterning may be effective in controlling astrocyte interaction with implant materials.

Animals↗
PubMed1999

Retinal pigment epithelial cell function on substrates with chemically micropatterned surfaces.

Model substrates with desired chemical micropatterns were fabricated using a microcontact printing technique. The substrate surfaces contained organized arrays of circular glass domains with a diameter of either 10 or 50 microm surrounded and separated by regions modified with octadecyltrichlorosilane (OTS) self-assembled monolayers (SAMs). The effects of surface patterning on in vitro cell attachment, proliferation, morphology, and cytoskeletal organization were evaluated using a human retinal pigment epithelium (RPE) cell line. Both micropatterns affected initial RPE cell attachment, limited cell spreading, and promoted the characteristic cuboidal cell morphology throughout the culture period. In contrast, RPE cells on plain glass control were elongated and appeared fibroblast-like prior to confluence. In addition, cells seeded at 30,000 cell/cm2 on the patterned surfaces maintained a normal pattern of actin and cytokeratin expression, and formed confluent monolayers within 4 days of culture. The cell density increased about 30-fold on both micropatterns by day 7. These results show that it is feasible to control RPE cell shape and expression of differentiated phenotype using micropatterned surfaces.

Actins↗
PubMed1998

Ulcerative colitis in young adults. Complexities of diagnosis and management.

Ulcerative colitis should be considered in any patient with chronic diarrhea or rectal bleeding. Diagnosis depends on a combination of findings from physical, laboratory, endoscopic, and histopathologic examinations, together with the exclusion of other causes and continued observation over time. The mainstays of treatment are sulfasalazine for mild to moderate disease and corticosteroids for moderate to severe disease. Side effects of sulfasalazine, due to the sulfa moiety of the drug, limit its use in some patients. Newer, sulfa-free 5-ASA agents, although expensive, are appropriate for patients who cannot tolerate sulfasalazine. Refractory ulcerative colitis is best treated surgically. Most patients require maintenance therapy with sulfasalazine or a sulfa-free 5-ASA preparation. Cancer risk is increased in patients with long-standing ulcerative colitis.

Adrenal Cortex Hormones↗
PubMed1998

[Progressive noma: apropos of 27 cases seen at the National Hospital Center of Ouagadougou].

This retrospective study objects to report epidemiological profile, clinical display and take care of progressive noma at the National Hospital Center of Ouagadougou. We assign the term noma to the gangrenous gingivo-stomatitis occurring in a prone environment, leading in a few days into a sharp ulcer in the soft parts, accompanied by halitosis. This definition excludes noma like-lesions. 27 cases have been observed in the ENT department and the Paediatrics between 1991 and 1995. They were 17 boys and 10 girls aging between 2 and 8 years and most of them coming from families with modest income (76%). The consultation delay averaged 8 days. The research for associated pathologies showed 63% energizing and protein malnutrition. We only observed unilateral localisations and no case of extra-facial one. At the stage we received our patients, the gangrenous was formed and the aspect evoked noma right away. Quite a lot needs to be done for precocious diagnosis because it is at the beginning phase that best evolution is obtained. Even though no evidence of the responsibility of a specific pathogenic germ was established so far, nevertheless, the assumption that has more support remains that of a bacterial infection in a prone environment. The vital prognosis of the progressive noma appears to be much linked with intensive care and feeding again. The hope to see this poverty-linked pathology under control is essentially based on prevention: medical population information, medical personnel's awareness for early diagnosis and best take care of these patients, improvement of the living conditions of the people and the health care services.

Burkina Faso↗
PubMed1997

Preferential glial cell attachment to microcontact printed surfaces.

Microcontact printing is introduced as a method for fabricating test surfaces for attachment of cells to chemically patterned silicon surfaces. Tests with astroglial cells indicate that cells attach to microcontact printed surfaces similarly to surfaces produced by traditional photolithographic methods. Astroglial cells attach selectively to 50 microns wide bars of N1[3-(Trimethoxysilyl)propyl]diethylenetriamine (DETA) self-assembled monolayers (SAMs) on surfaces prepared using variable width spaces generated from microcontact printing with octadecyltrichlorosilane (OTS) as the ink. Our results demonstrate that microcontact printing provides an effective and rapid method for routine production of patterned self-assembled monolayers that can be used for directing cell attachment and studying cell morphology.

Amines↗
PubMed1996

Human immunodeficiency virus-1 (HIV-1) gp120 superantigen-binding serum antibodies. A host factor in homosexual HIV-1 transmission.

HIV-1 gp120 is an immunoglobulin superantigen which can bind to preimmune serum Ig. We hypothesize that levels of such preimmune antibodies vary in the population and might affect host resistance or susceptibility to viral transmission. This study tests two predictions: (a) levels of preimmune anti-gpl20 Igs are a polymorphic trait; and, (b) these levels are correlated with resistance or susceptibility to HIV-1 transmission. The first prediction was confirmed in a longitudinal study of a low-risk seronegative population. In this group, levels of both endogenous anti-gpl20 IgM and IgG varied widely, but were characteristic and stable for each individual. The second prediction was addressed in a study of participants of the Multicenter AIDS Cohort Study, in which men "susceptible" and "resistant" to HIV infection were identified based on numbers of sexual partners and eventual seroconversion. Specimens consisted of archival sera obtained > 2 yr before seroconversion. Men in the susceptible population (low-risk seroconverters) were distinguished by low levels of anti-gpl20 IgG. We conclude that the level of preimmune anti-gpl20 IgG is a polymorphic population trait, and low levels are a potentially specific and significant factor in homosexual transmission of HIV infection.

Acquired Immunodeficiency Syndrome↗