Is 48 hours conditioning prior to testing necessary / A. J. Long in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 87, N° 1 (01-02/2003)  

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 87, N° 1 (01-02/2003) Titre : Is 48 hours conditioning prior to testing necessary Type de document : texte imprimé Auteurs : A. J. Long, Auteur ; C. B. Wood, Auteur ; D. A. Langridge, Auteur Année de publication : 2003 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Conditionnement Cuir Index. décimale : 675 Technologie du cuir et de la fourrure Résumé : The aim of this work is to determine whether it is feasible to reduce the time required to condition leather prior to physical testing, whilst still ensuring accurate and reliable results. The method SLP 3 / IUP 31 describing the conditioning of leather was first published as an official method in the Journal of the Society of Leather Technologists and Chemists in 1958.2 (It was previously published for comment in 19493). There has been little change since this date. The latest version does acknowledge that in some cases there is the need for rapid conditioning, although this is not widely used in industry due to the possibility of arbitration which still requires the full 48 hour process (suggesting that the rapid method may not be producing the same results as the standard conditions). The aim therefore is to reduce the time required to carry out some key tests, but not necessarily to remove the requirement for the official standard. It is hoped that alternative options will be devised for those tanneries and test houses where 48 hours effective dead time prior to testing is a significant problem. A separate issue that is under discussion is the use of the different conditions 23oC, 50%RH. Whilst it is acknowledged that there are issues of importance in this area, these have not been considered in this research. The work published here uses the UK standard of 20oC, 65% RH. Note de contenu : - Aims of this work - Experimental Work and Results : Determination of the significance of conditioning - Evaluation of the optimum duration for conditioning - Evaluation of the moisture xontent of leather - Investigation of accelerated conditioning - Table 1 : The Effect of conditioning on the tear strength of leather - Table 2 : Effect of conditioning on water vapour absorption of leather - Table 3 : Effect of pre-drying on leather conditioning En ligne : https://drive.google.com/file/d/1ojBnyo0_WPpfRkUXrY-2ixO3stTAxXDO/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=39807 [article]

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Microscopy methods to study fat cells : Part 1 : characterisation of ovine cutaneous lipids using microscopy / V. L. Addy in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 85, N° 1 (01-02/2001)  

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 85, N° 1 (01-02/2001) . - p. 6-15 Titre : Microscopy methods to study fat cells : Part 1 : characterisation of ovine cutaneous lipids using microscopy Type de document : texte imprimé Auteurs : V. L. Addy, Auteur ; Anthony D. Covington, Auteur ; D. A. Langridge, Auteur ; A. Watts, Auteur Année de publication : 2001 Article en page(s) : p. 6-15 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Adipocytes Cuirs et peaux -- Analyse Cuirs et peaux de bovins Histochimie Lipides Microscopie Index. décimale : 675 Technologie du cuir et de la fourrure Résumé : Microscopy has been employed to study cutaneous lipids. In particular, light microscopy in conjunction with histochemical labelling techniques and confocal microscopy have been used to determine the chemical basis of the lipid moieties and provide qualitative information regarding the extent to which lipids are deposited within the skin substrate. Furthermore a range of electron microscopy techniques, including a novel cryo-scanning electron microscopy technique, have been used to resolve the structure of the fat cell substrate. Due to inter and intra skin variation, there are difficulties associated with using intact skin as a model for studying adipocytes. Subcutaneous adipose tissue was therefore utilized for studying the morphology of component adipocytes using microscopy. Note de contenu : - Preparation for light microscopy - Histochemical staining methods - Confocal microscopy - Transmission electron microscopy - Cryo-scanning electron microscopy - Freeze fracture microscopy En ligne : https://drive.google.com/file/d/10w3NoQnq4UMVOAKLzo4wis8XO0g8u-dz/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=40588 [article]

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Microscopy methods to study fat cells - Part 2 : Study of the interaction of ovine cutaneous adipocytes with lipase enzymes using microscopy / V. L. Addy in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 85, N° 2 (03-04/2001)  

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 85, N° 2 (03-04/2001) . - p. 52-65 Titre : Microscopy methods to study fat cells - Part 2 : Study of the interaction of ovine cutaneous adipocytes with lipase enzymes using microscopy Type de document : texte imprimé Auteurs : V. L. Addy, Auteur ; Anthony D. Covington, Auteur ; D. A. Langridge, Auteur ; A. Watts, Auteur Année de publication : 2001 Article en page(s) : p. 52-65 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Adipocytes Analyse morphologique Cuirs et peaux -- Analyse Cuirs et peaux de moutons Enzymes Une enzyme est une protéine dotée de propriétés catalytiques. Pratiquement toutes les biomolécules capables de catalyser des réactions chimiques dans les cellules sont des enzymes ; certaines biomolécules catalytiques sont cependant constituées d'ARN et sont donc distinctes des enzymes : ce sont les ribozymes. Une enzyme agit en abaissant l'énergie d'activation d'une réaction chimique, ce qui accroît la vitesse de réaction. L'enzyme n'est pas modifiée au cours de la réaction. Les molécules initiales sont les substrats de l'enzyme, et les molécules formées à partir de ces substrats sont les produits de la réaction. Presque tous les processus métaboliques de la cellule ont besoin d'enzymes pour se dérouler à une vitesse suffisante pour maintenir la vie. Les enzymes catalysent plus de 5 000 réactions chimiques différentes2. L'ensemble des enzymes d'une cellule détermine les voies métaboliques qui peuvent avoir lieu dans cette cellule. L'étude des enzymes est appelée enzymologie. Les enzymes permettent à des réactions de se produire des millions de fois plus vite qu'en leur absence. Un exemple extrême est l'orotidine-5'-phosphate décarboxylase, qui catalyse en quelques millisecondes une réaction qui prendrait, en son absence, plusieurs millions d'années3,4. Comme tous les catalyseurs, les enzymes ne sont pas modifiées au cours des réactions qu'elles catalysent, et ne modifient pas l'équilibre chimique entre substrats et produits. Les enzymes diffèrent en revanche de la plupart des autres types de catalyseurs par leur très grande spécificité. Cette spécificité découle de leur structure tridimensionnelle. De plus, l'activité d'une enzyme est modulée par diverses autres molécules : un inhibiteur enzymatique est une molécule qui ralentit l'activité d'une enzyme, tandis qu'un activateur de cette enzyme l'accélère ; de nombreux médicaments et poisons sont des inhibiteurs enzymatiques. Par ailleurs, l'activité d'une enzyme décroît rapidement en dehors de sa température et de son pH optimums. Histochimie Lipases Les lipases sont des enzymes hydrosolubles capables d'effectuer l'hydrolyse de fonctions esters et sont spécialisées dans la transformation de triglycéride en glycérol et en acides gras (lipolyse). À ce titre, elles constituent une sous-classe des estérases. Microscopie Structure cellulaire (biologie) Index. décimale : 675 Technologie du cuir et de la fourrure Résumé : In Part 1 of this series, a range of microscopy techniques used to study the morphology of the fat cell substrate was described, with a view to developing a better understanding of the degreasing process. This paper discusses how these techniques have been used to study the interaction between the ovine adipocyte substrate with lipid hydrolases. Microscopy has revealed that, under alkaline conditions, the triacylglycerol lipase is able to penetrate the fat cell to effect hydrolysis which is calcium dependent. A striking consequence of this reaction is the morphological changes associated with the adipocyte plasma membrane. These structural changes are thought to be due to the contraction of the plasma membrane, caused by the depletion of the intracellular lipid. The effect of PLA, hydrolysis on the adipocyte substrate is significant, but mechanistically different to that seen with the triacylglycerol lipase. The deformation of the cell is targeted rather than pervasive, which implies that the phospholipids within the plasma membrane are being hydrolysed. causing pitting and localized deformation of the membrane. These studies demonstrate that gross cellular changes are associated with the hydrolysis of ovine cutaneous adipocyte derived lipid. This is important evidence to suggest that lipid hydrolases can be used to target and hydrolyse ovine storage lipid. Note de contenu : - EXPERIMENTAL DETAILS : Cryo-scanning electron in microscopy - Transmission electron microscopy - Freeze fracture microscopy - Laser scanning confocal in microscopv - Phospholipase studies - RESULTS : Study of the interaction of the lipase enzyme with the adipocyte substrate - 1-Histochemical labelling of free fatty acids - Cryo—scanning electron microscopy studies - Transmission electron microscopy studies - Freeze fracture microscopy studies - Confocal scanning microscopy - Phospholipase studies - Table 1 : Adipocyle cellular structure and histochemical observations for the experimental conditions - Table 2 : Adipocyte morphology after treating with lead ions to stain the fatty acids En ligne : https://drive.google.com/file/d/1wiW1JrOwLWuHDFpsZwszHJaA9KwKPMSx/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=40413 [article]

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The use and subsequent treatment of surfactants for leather processing / Rumon A. Hankey in JOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA), Vol. XCVI, N° 6 (06/2001)  

[article]  inJOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (JALCA) > Vol. XCVI, N° 6 (06/2001) . - p. 205-213 Titre : The use and subsequent treatment of surfactants for leather processing Type de document : texte imprimé Auteurs : Rumon A. Hankey, Auteur ; V. L. Addy, Auteur ; K. Senior, Auteur ; D. A. Langridge, Auteur ; Warren Bowden, Auteur ; W. Scholz, Auteur Année de publication : 2001 Article en page(s) : p. 205-213 Note générale : Bibliogr. Langues : Américain (ame) Index. décimale : 675 Technologie du cuir et de la fourrure Résumé : The appropriate choice of the type of surfactant for degreasing is very important. In today's environment, pressures from 'green' issues limit the choice of type of degreaser used. The method of comparing degreasers for use in bovine soaking and liming systems is discussed along with the screening of suitable alternatives to Nonyl Phenol Ethoxylate based degreasers. The volume of the grease emulsion in the waste water can be reduced by the use of ultrafiltration. Alkyl phenol ethoxylates function as effective surfactants. More specifically, nonyl phenol ethoxylates (NPE) exhibit excellent wetting and emulsification properties which has resulted in their use as cost effective detergents for the leather industry. Recently, however, their use has been questioned due to environmental concerns. The objective of this study was, therefore, to evaluate commercially available alternative surfactants to nonyl phenol ethoxylate (NPE) based products for the removal of dermal fat from bovine hides. The performance of the surfactants was tested, initially using a model system based on extracted bovine subcutaneous lipid. Subsequently the best four products (tested under the conditions of the assay) were evaluated in small-scale trials. The assay system proved effective for differentiating between good and poor emulsifiers of bovine fat. Four products were selected for exhibiting performance equal to the NPE based products.These products were subsequently evaluated in soaking and liming trials in the production of bovine wet blue. Each of the surfactants gave performance equivalent to that given by the NPE based products. However, the levels of intra-dermal fat were low, in the region of 1.0% and meaningful quantitative analysis was therefore difficult. This suggests that problematic degreasing in bovine processing may originate from poorly fleshed hides rather than residual intra-dermal fat. There was no evidence of redeposition of fat into the wet blue. In conclusion, a number of surfactant products that give acceptable removal of hide fat and contain no NPE have been identified. Their use in full-scale production has not been evaluated within the scope of this project. Two techniques for determining the amount of surfactant present in liquors and leather have been evaluated and developed. The combination of these analytical techniques may enable further optimisation of processes with a view to allowing an overall reduction in offers of surfactants used. The treatment of surfactants in the waste water treatment plant is difficult. Progress has been made by the use of ultrafiltration to remove up to approximately 90% of grease-emulsion from waste streams. En ligne : https://drive.google.com/file/d/1tGm3R7dvS2HHvAyZLPsZToUHFHE84FP-/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=4372 [article]

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