Theory of Fluid Lubrication of Hydrogels and Articular Cartilage during Compression Under an Applied Load

2012 ◽  
Vol 1418 ◽  
Author(s):  
J. B. Sokoloff
Keyword(s):  
Articular Cartilage ◽  
Experimental Studies ◽  
Solid Material ◽  
Interface Region ◽  
Fluid Viscosity ◽  
Asperity Height ◽  
Coated Surfaces ◽  
Fluid Pressurization ◽  
Almost All

ABSTRACTA fluid lubrication model for articular cartilage was put forward by Mc Cutchen, in which a high percentage of the load is supported by fluid pressurization in the interface region separating the two cartilage coated surfaces as the cartilage is compressed under load. This reduces the friction by reducing the percentage of the load which is carried by solid material in the cartilage. For two bones which are in contact in a healthy joint, which are each coated by a layer of cartilage whose thickness is much smaller than its lateral dimensions, it will be argued that since the bone is impervious to fluid flow in healthy joints, almost all of the fluid that is expressed from the cartilage under load flows through the interface region, where it supports part of the load. This is in contrast to previous theoretical and in vitro experimental studies of this problem, in which most of the fluid does not flow into the interface. It is shown that for mean asperity height small compared to a length scale (which depends on the cartilage or hydrogel permeability, the fluid viscosity and the dimensions of the cartilage or hydrogel) a large percentage of the load is supported by fluid pressurization.

scholarly journals Articular Cartilage Wear Characterization With a Particle Sizing and Counting Analyzer

2012 ◽  
Author(s):  
Sevan R. Oungoulian ◽  
Orian Bortz ◽  
Kristin E. Hehir ◽  
Kaicen Zhu ◽  
Clark T. Hung ◽  
...  
Keyword(s):  
Articular Cartilage ◽  
Friction Coefficient ◽  
Wear Debris ◽  
Polyethylene Wear ◽  
Quantitative Measurements ◽  
Diarthrodial Joints ◽  
Cartilage Wear ◽  
Tangential Forces ◽  
Fluid Pressurization

The primary function of articular cartilage is to serve as the bearing material in diarthrodial joints, transmitting loads while minimizing friction and wear. The friction coefficient of cartilage has been characterized extensively in the literature, using standard measurements of normal and tangential forces acting across a sliding interface [1]. However, quantitative measurements of cartilage wear have proven to be more challenging, with only a few studies having reported such measurements. The primary quantitative approaches proposed to date include biochemical assaying of cartilage and test solutions [2], and characterization of changing articular layer thickness [3] and surface roughness [4]. One study examining polyethylene wear debris in hip arthroplasty reported the use of an automated particle analyzer [5]. The aim of this study was to test the hypothesis that latest-generation particle analyzers are capable of detecting cartilage wear debris generated during in vitro loading experiments that last 24 h or less, by producing measurable content significantly above background noise levels. The longer-term objective of our studies is to test the hypothesis that elevated interstitial fluid pressurization, which is known to reduce the friction coefficient of cartilage [6], also reduces cartilage wear.

scholarly journals Experimental studies on the differentiation of embryonic tissues growing in vivo and in vitro .—I. The development of the undifferentiated limb-bud (a) when subcutaneously grafted into the post-embryonic chick and (b) when cultivated in vitro

1926 ◽  
Vol 99 (698) ◽  
pp. 340-366 ◽  
Keyword(s):  
Preliminary Investigation ◽  
Experimental Studies ◽  
Limb Bud ◽  
Posterior Limb ◽  
Embryonic Tissues ◽  
Embryonic Limb ◽  
Almost All ◽  
Normal Standards

One method by which the problem of the differentiation of animal tissues may be approached is by studying the behaviour of simple embryonic tissues when growing in an abnormal environment, such as that produced by grafting into atypical situations in vivo or by cultivation in vitro . It is along these lines that the investigations of the present writers are being conducted. The work so far completed, the results of which are recorded in the present communication, consists of a study of the development of the undifferentiated, embryonic limb-bud of the fowl when grafted subcutaneously into a postembryonic chick and when cultivated vitro. A preliminary investigation of the histogenesis of cartilage and bone in the limbs of the embryonic fowl was carried out by one of the writers (Fell, 1925) in order to provide normal standards with which to compare the experimental material. Rous (1910, 1911), Fichera (1909) and many others have successfully grafted foœtal and embryonic tissues into young and adult animals, usually in connection with the study of tumour growth ; a bibliography and summary of the earlier work is given in Fichera’s paper. Almost all the work on the development of grafts of the undifferentiated limb-buds has been carried out on the embryonic Amphibia by Braus, Harrison (1907, 1918, 1921), Detweiler (1918, 1925), Nicholas (1924) and others. Spurting (1923) describes a case of accidental but successful autotransplantation of the posterior limb-bud in a fowl embryo. Murray and Huxley (1925) record two experiments in which part of the limb-bud of a four-days’ embryo was successfully grafted on to the chorioallantoic membranes ; in one case “ a highly differentiated and very easily recognizable femur ” showing early ossification was found after 5 days’ growth.

Experimental Studies on a Recombinant Hirudin, CGP 39393

1991 ◽  
Vol 65 (04) ◽  
pp. 355-359 ◽  
Author(s):  
E Gray ◽  
J Watton ◽  
S Cesmeli ◽  
T W Barrowcliffe ◽  
D P Thomas
Keyword(s):  
Thrombin Generation ◽  
Bleeding Time ◽  
Thrombus Formation ◽  
Experimental Studies ◽  
Venous Stasis ◽  
Antithrombotic Agent ◽  
Recombinant Hirudin ◽  
Excessive Bleeding ◽  
Generation Test

SummaryThe in vitro anticoagulant activities of recombinant desulphatohirudin (r-hirudin) were studied in the activated partial thromboplastin time (APTT) and the thrombin generation test : systems. In the APTT at concentrations below 5 μg/ml, r-hirudin showed a dose-response curye. At concentrations above 5 μg/ml, the plasma became unclottable, but in the thrombin generation test , at least 10 μg/ml of r-hirudin was required for full inhibition of thrombin generation. The antithrombotic effect was assessed using a rabbit venous stasis model; 150 μg/ml r-hirudin completely prevented thrombus formation at 10 and 20 min stasis. At antithrombotic dose, the mean bleeding time ratio measured in a rabbit ear template model, was not prolonged over control values. At higher doses, the bleeding time ratios were higher than those observed for the same dosage of heparin. These data indicate that while r-hirudin is an effective antithrombotic agent, antithrombotic doses have to be carefully titrated to avoid excessive bleeding.

IN VITRO METHODS FOR THE STUDY OF THE ADENOHYPOPHYSIAL FUNCTIONS TO SECRETE GONADOTROPHIN

1971 ◽  
Vol 68 (1_Suppl) ◽  
pp. S27-S40 ◽  
Author(s):  
T. Kobayashi ◽  
T. Kigawa ◽  
M. Mizuno ◽  
T. Watanabe
Keyword(s):  
Cell Culture ◽  
Organ Culture ◽  
Cultured Cells ◽  
Cell Sheet ◽  
Short Term ◽  
Hypothalamic Extract ◽  
Numerous Cell ◽  
Single Cell Culture ◽  
Almost All

ABSTRACT There are several in vitro methods to analyse the function of the adenohypophysis or the mechanisms of its regulation. The present paper deals with single cell culture, organ culture and short term incubation techniques by which the morphology and gonadotrophin-secreting function of the adenohypophysis were studied. In trypsin-dispersed cell culture, the adenohypophysial cells showed extensive propagation to form numerous cell colonies and finally develop into a confluent monolayer cell sheet covering completely the surface of culture vessels. Almost all of the cultured cells, however, became chromophobic, at least at the end of the first week of cultivation, when gonadotrophin was detectable neither in the culture medium nor in the cells themselves. After the addition of the hypothalamic extract, gonadotrophin became detectable again, and basophilic or PAS-positive granules also reappeared within the cells, suggesting that the gonadotrophs were stimulated by the extract to produce gonadotrophin. In organ culture and short term incubation, the incorporation of [3H] leucine into the adenohypophysial cells in relation to the addition of hypothalamic extract was examined. It was obvious that the ability to incorporate [3H] leucine into the gonadotrophs in vitro was highly dependent upon the presence of the hypothalamic extract.

In Vitro Immunodetection of Prothymosin Alpha in Normal and Pathological Conditions

2020 ◽  
Vol 27 (29) ◽  
pp. 4840-4854 ◽  
Author(s):  
Chrysoula-Evangelia Karachaliou ◽  
Hubert Kalbacher ◽  
Wolfgang Voelter ◽  
Ourania E. Tsitsilonis ◽  
Evangelia Livaniou
Keyword(s):  
Mammalian Cells ◽  
Therapeutic Potential ◽  
Prothymosin Alpha ◽  
Disease States ◽  
Leading Role ◽  
Tissue Extracts ◽  
Biologic Response ◽  
Health And Disease ◽  
Almost All

Prothymosin alpha (ProTα) is a highly acidic polypeptide, ubiquitously expressed in almost all mammalian cells and tissues and consisting of 109 amino acids in humans. ProTα is known to act both, intracellularly, as an anti-apoptotic and proliferation mediator, and extracellularly, as a biologic response modifier mediating immune responses similar to molecules termed as “alarmins”. Antibodies and immunochemical techniques for ProTα have played a leading role in the investigation of the biological role of ProTα, several aspects of which still remain unknown and contributed to unraveling the diagnostic and therapeutic potential of the polypeptide. This review deals with the so far reported antibodies along with the related immunodetection methodology for ProTα (immunoassays as well as immunohistochemical, immunocytological, immunoblotting, and immunoprecipitation techniques) and its application to biological samples of interest (tissue extracts and sections, cells, cell lysates and cell culture supernatants, body fluids), in health and disease states. In this context, literature information is critically discussed, and some concluding remarks are presented.

Effects of in vitro low oxygen tension preconditioning of buccal fat pad stem cells on in Vivo articular cartilage tissue repair

Life Sciences ◽  
2021 ◽  
pp. 119728
Author(s):  
Fatemeh Dehghani Nazhvani ◽  
Leila Mohammadi Amirabad ◽  
Arezo Azari ◽  
Hamid Namazi ◽  
Simzar Hosseinzadeh ◽  
...  
Keyword(s):  
Stem Cells ◽  
Articular Cartilage ◽  
Tissue Repair ◽  
Cartilage Tissue ◽  
Low Oxygen ◽  
Fat Pad ◽  
Buccal Fat Pad ◽  
Low Oxygen Tension
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