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C Collombel

Publications and source records attributed to C Collombel.

At least 19 recordsLinked to original sources
PubMed1995

Keratinocyte extracellular matrix-mediated regulation of normal human melanocyte functions.

Active roles of cell-cell interaction between melanocytes and neighboring keratinocytes for the regulation of melanocyte functions in the skin have been suggested. We examined substantial regulatory mechanisms of keratinocyte extracellular matrix (kECMs) for normal human melanocyte functions without direct cell-cell contact. We specially devised kECMs from proliferating or differentiating keratinocytes and further treated them with environmental stimulus ultraviolet B (UVB) for skin pigmentary system. Normal human melanocytes (NHM) were cultured on the various keratinocyte ECMs and initially the effects of the kECMs upon melanocyte morphology (dendrite formation and extension), growth, melanin production and expressions of pigmentation-associated protein (MEL-5) and proliferation-associated protein (proliferating cell nuclear antigen; PCNA/cyclin) were studied. Then we compared the effects of these cell-matrix interactions with those of direct melanocyte-keratinocyte, cell-cell contact in co-culture on melanocyte functions. Melanocytes cultured on any types of the kECMs that were tested significantly extended dendrites more than that on plastic cell culture dish without kECM (control). Melanocytes cultured on any types of the kECMs that were tested significantly extended dendrites more than that on plastic cell culture dish without kECM (control). Melanocytes cultured on the kECM prepared from UVB irradiated differentiating keratinocytes resulted in 219% increase in the number of dendrites. The growth of melanocytes on kECMs was also stimulated up to 280% of control. The kECM produced by proliferating keratinocytes had a more significant effect on the growth than kECM from differentiating keratinocytes. This melanocyte growth stimulating effect was decreased with kECM from UVB treated differentiating keratinocytes. The melanin content per melanocyte was constant on any of the kECMs.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗
PubMed1993

Modulation of normal human melanocyte dendricity by growth-promoting agents.

Dendrite formation and extension, which comprise a characteristic morphology of human normal melanocytes in the skin, represent one of the functional activities of melanocytes, the ability to transfer melanosomes into neighboring keratinocytes. However, the morphology of the melanocyte in vitro is usually quite different from that observed in vivo. it is probably due to the hyperproliferative condition of the melanocytes in culture. No studies have ever compared the effects of a single factor on both dendricity and proliferation at the same time. Therefore, we have compared the effects of six growth-promoting agents commonly used for melanocyte cultures on dendrite formation and proliferation. The addition of agents that increase the intracellular levels of cyclic adenosine monophosphate (cAMP)--dibutyryl cyclic adenosine monophosphate (db cAMP; 1 mM) or isobutylmethyl xanthine (IBMX; 0.1 mM)--had a strong effect on dendrite formation and a negative effect on proliferation. This was especially true with db cAMP. In the presence of 2% or 5% of heat-inactivated fetal bovine serum (FBS), dendrite formation was significantly increased as was proliferation. The number of dendrites was decreased in the culture with 12-o-tetradecanoylphorbol-13-acetate (TPA), but cell growth was slightly increased. With human recombinant basic fibroblast growth factor (bFGF) (0.5, 1.0 ng/ml) in the presence of bovine pituitary extract (BPE) (60 micrograms/ml), cell growth was increased. With 2 ng/ml of bFGF, however, a strong inhibitory effect on proliferation was observed. However, dendrite formation was constant at all concentrations of bFGF tested (0.5, 1.0 or 2.0 ng/ml) with BPE (30 or 60 micrograms/ml). In this study, we have demonstrated that dendrite formation was suppressed by the reagents that stimulate melanocyte proliferation, and vice versa, with the only exception being heat-inactivated FBS. Both dendrite formation and proliferation were induced by the heat-inactivated FBS. This approach is crucial to the development of an adequate culture system for proliferation and/or dendrite formation of normal human melanocytes. It is necessary to keep these aspects in mind as we further investigate the biology of melanocytes, especially the cell-to-cell interactions between melanocytes and keratinocytes, involved in melanogenesis and melanin pigmentation in vivo. This study also provides practical and important information for a future reconstitutive skin system composed of melanocytes, keratinocytes, and fibroblasts in a single culture medium.

1-Methyl-3-isobutylxanthine↗
PubMed1992

Cytotoxicity evaluation of antiseptics and antibiotics on cultured human fibroblasts and keratinocytes.

Infection is the greatest problem in burn patients and topical antimicrobial agents must be chosen with great care, especially when cultured skin is grafted. We examined the cytotoxic effect of six antiseptics and six antibiotics commonly used on cultured human fibroblasts and keratinocytes. Cultured cells were exposed for 15 min to Hibitane (chlorhexidine), Biseptine (chlorhexidine+benzalkonium chloride+benzylic alcohol), Benzalkonium Chloride, Yellow Betadine (polyvidone-iodine+nonoxinol), Betadine Scrub (polyvidone-iodine+quaternary ammonium) and Green Betadine (polyvidone-iodine) and viability was determined using the MTT test. At therapeutic concentrations all the antiseptics are cytotoxic for fibroblasts and keratinocytes. Additionally the cells were exposed for 48 h to vancomycin, colistin, amikacin, imipeneme, pefloxaxin, piperacillin and cell viability was determined using the MTT test. The concentrations of antibiotics corresponding to the plasma peak obtained after therapeutic application were not cytotoxic to the tested cells. The CD50 was much higher than the MIC (from 125 to 875 times for keratinocytes and from 1400 to 5900 times for fibroblasts). These data suggest that commonly applied antiseptics must not be used before grafting cultured skin grafts. After grafting any infection can be controlled with topical applications of appropriate antibiotics.

Anti-Bacterial Agents↗
PubMed1991

European multicentre evaluation of the Du Pont Dimension 380 under the auspices of the European Group for the Evaluation of Analytical Systems in Laboratory Medicine (EGE-Lab).

The Clinical Chemistry Analyzer Dimension 380 manufactured by Du Pont de Nemours was tested in a multicentre evaluation according to the guide-lines of the European Committee for Clinical Laboratory Standards (ECCLS) and in part to the protocol of the Société Française de Biologie Clinique (SFBC). The instrument and the reagents were evaluated as a system, since both reagents and reagent cartridges are specifically designed for the instrument. Fourteen analytes including electrolytes, substrates and enzymes were tested. The evaluators summarized their experience as follows: 1. All parameters tested yield results comparable to established procedures. 2. Very good performance of the ion-selective-electrode unit. 3. The imprecision data of the system are, for most parameters, between 1 and 4% CV and thus equal to or better than those of the instruments compared. 4. No reagent or sample carry-over was detected after a minor modification of the instrument. 5. The linearity of Dimension test methods in general covers the range stated by the manufacturer. 6. Very good stability of the calibration curves (up to 2 months). 7. Good practicability of the whole system, including handling of reagents and a very user-friendly software.

Blood Chemical Analysis↗
PubMed1990

Characterization of skin reconstructed on a chitosan-cross-linked collagen-glycosaminoglycan matrix.

Reconstruction of skin requires both the dermal and epidermal equivalent of the skin. We have developed a reconstructed skin composed of two compartments: (1) a dermal equivalent comprising an acellular dermal substrate populated by foreskin fibroblasts and (2) an epidermis regenerated from normal human keratinocytes seeded onto the dermal equivalent. The dermal substrate contains type I and III collagen and glycosaminoglycans (GAGs) cross-linked by chitosan. Fibroblasts seeded into the porous structure of the dermal substrate provide a dermal equivalent suitable to support epidermal cells. Keratinocytes attach quickly, exhibit mitotic activity and form a continuous and stratified epidermis. After 2 weeks of culture, histological sections show a basal layer with cuboidal cells attached to the dermal equivalent and several suprabasal cell layers including the stratum corneum. Transmission electron microscopy revealed the cell membrane densification (hemidesmosomes) at the dermoepidermal junction; however, the lamina densa was found discontinuous at this stage. We noted the presence of lipid vesicles in spinous layer and keratohyalin granules in granular layer. The epidermal differentiation was complete terminal with the stratum corneum containing several layers of corneocytes filled with tonofilaments. Reconstructed skin, based on our chitosan-cross-linked collagen-GAG matrix is morphologically equivalent to normal human skin and should thus provide a useful tool for in vitro toxicological studies as well as a suitable wound covering for the treatment of patients with severe burns.

Animals↗
PubMed1989

[Development of non-cellular dermis: a step towards a total artificial skin].

In large cutaneous defects due to severe burns, dermal mesenchyme healing has to be controlled in order to avoid granulation tissue that rapidly leads to important contractures and hypertrophic scars. We report a study about the use of an artificial dermis made of human collagen (I and III) and several glycosaminoglycans. This artificial dermis was grafted on Sprague-Dawley rats after a 9 cm2 skin excision on the back. An identical control area was made just under it, on the same animal. The animals were killed on day 2, 7, 14, 21, 30 and different parameters were studied: clinical study, bacteriological study, histopathological appearance, scanning and transmission electron microscopy, immunological study, physical parameters, UV absorption. Direct and indirect cytotoxicity tests, performed on cell cultures showed no change in the morphology and of the growth of the keratinocytes or of the fibroblasts. A biocompatibility study showed on the early days (day 2, 7, 14) that adherence of artificial dermis to the underlying tissue was good. There was virtually no bacterial colonization. Ultrastructural study showed an important cellular colonization, with an inflammatory appearance at the beginning. After a while, fibroblasts appeared, with synthesis of neocollagen fibers as early as the second week. Histological study showed neovessels in the artificial dermis. Later (day 21, 30) the inflammation was less severe and the amount of endogenous collagen increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Artificial Organs↗
PubMed1986

[Tissue and blood ferritins and isoferritins].

Ferritins which can store excess iron are localised principally in tissue. Ferritins have on apoprotein shell which is composed of 24 sub-units, from 2 types of sub-units: "H" (molecular weight about 21 000) and "L" (molecular weight about 19 000) that assemble in different proportions and give multiple forms. Protein pattern depends on tissue nature. Since 1972, radio-immunology assays have shown very low serum ferritin levels. There is a good correlation between these levels and the amount of storage iron in the body. However it was demonstrated that elevation of serum ferritin could also occur without iron metabolism trouble by various mechanisms.

Chemical Phenomena↗
PubMed1985

On the choice of an organization for a pathology laboratory.

The study describes an approach to the optimal allocation of sample analysis in a pathology laboratory. The paper consists of three parts: identification of the problem to be resolved; description of the model and application of the model to the organization of a specific laboratory.

Blood Chemical Analysis↗
PubMed1985

Liquid-phase reactions started by rehydrating lyophilized reagents in a centrifugal analyzer.

In the disposable rotor of the SAM microcentrifugal analyzer, various lyophilized reagents are predistributed in 24 33-microL cuvets, for determination of multiple analytes in one specimen (e.g., for patient profiles). We evaluated a prototype of this system, which can be used at 25, 30, or 37 degrees C; absorbance readings at 340, 405, and 500 nm varied linearly up to 2.0 A. Starting the reactions by rehydrating the reagents with diluted serum is adequate because absorbance readings do not begin until 180 s after initiating the rehydration. Analytical performances of kinetic determinations at 30 degrees C showed good accuracy and correlation with other methods for creatine kinase, amylase, aspartate aminotransferase, and gamma-glutamyltransferase. Kinetic determinations for urea, and equilibrium determinations with blank corrections for glucose, cholesterol, and triglycerides gave excellent results for glucose and correct results for the other analytes. This compact analyzer combines the analytical performances of a centrifugal analyzer with the practicability of instruments having predistributed reagents.

Centrifugation↗
PubMed1983

Screening for neonatal Duchenne muscular dystrophy by bioluminescence measurement of creatine kinase in a blood sample spotted on paper.

Neonatal screening for Duchenne-type muscular dystrophy is greatly simplified by use of a new bioluminescence procedure for creatine kinase. The blood of newborn myopathic children consistently showed increased activity. The improved method permits the analysis from a dried sample of whole blood spotted on filter paper; it shows high correlation with existing procedures and is highly specific and precise. The use of the improved method in a screening program involving 158 000 newborns is reviewed. We find a prevalence of 1/5929 living eighth-day boys.

Adenosine Triphosphate↗
PubMed1975

[Determination of glomerular and tubular clearance in children without urine collection].

The determination of glomerular and tubular clearance in a child was carried out by using a method excluding urine collection, with a continuous intravenous infusion of polyfructosan and para-amino-hippuric acid. A loading injection followed by a continuous perfusion provides a constant plasmatic level 150 minutes after the beginning of the study.

Aminohippuric Acids↗
PubMed1975

[Study of the pathogenic mechanism of hypocalcemia in primary hypomagnesemia. Demonstration of a blockage of the mechanism of release of parathyroid hormone].

Parathyroid function and peripheral responsiveness to parathyroid hormone were studied during magnesium dependent hypocalcemia in a 5 years old boy with primary hypomagnesemia. The bone system and the kidneys were responsive to exogenous bovine parathyroid extracts as demonstrated by the normalisation of the calcemia and the increase of urinary cyclic AMP, phosphorus and hydroxyproline. Low levels of serum immunoreactive parathyroid hormone gave also clear indication of impaired parathyroid function. By contrast intravenous injection of magnesium sulfate induced an instantaneous and very sharp increase of serum immunoreactive parathyroid hormone as shown by levels well above the normal range one minute after the injection ; this was followed by a regular decrease of hormonal levels reaching the normal range one hour later. This finding clearly demonstrates that severe magnesium depletion induces impaired parathyroid hormone release in man.

Child, Preschool↗
PubMed1975

[A form of late propionic acidemia].

Report of 3 cases of propionic acidemia which concern one boy (O.M.) in whom a formed diagnosis of hyperglycemia with ketosis had been established, and two sisters (C.V. and K.V.) of another family. The activities of propionyl-CoA carboxylase in O.M. and C.V. fibroblasts were reduced to 4.5 and 2.5% of control. After two severe metabolic crisis, at 6 and 44 months of age, O.M. has at the present time (11yrs) a normal psychical development, and very few neurological disorders. Propionic acidemia was manifested only at 34 months of age in C.V. with a very severe crisis of acidoketosis with hypoglycemia, leading to neurological sequellae which are still important at 56 months of age. The disease was entirely latent in K.V. at 26 months, when the diagnosis was proven; it remains latent at 40 months. These case reports represent a special form of propionic acidemia with late clinical expression. Biological evolution does not seem to be affected by prolonged administration of biotine.

Acidosis↗