Biomedical subjects

K Athanasiou

Publications and source records attributed to K Athanasiou.

At least 19 recordsLinked to original sources

PubMed2006

Effects of ageing on the biomechanical properties of rat articular cartilage.

Previous studies have demonstrated that male Sprague Dawley (SD) rats experience age-related bone loss with the same characteristics as that in ageing men. As articular cartilage, like bone, is a critical component of the health and function of the musculoskeletal system, the authors hypothesized that articular cartilage in the untreated male SD rats could be a suitable model for studying the age-related deterioration of articular cartilage in men. To test this hypothesis, male SD rats were killed at between 6 and 27 months. The right femur of each rat was removed. The effects of ageing on the structural integrity of the distal femoral articular cartilage were studied by biomechanical testing with a creep indentation apparatus. The aggregate modulus, Poisson's ratio, permeability, thickness, and percentage recovery of articular cartilage were determined using finite element/non-linear optimization modelling. No significant differences were observed in these biomechanical properties of the distal femoral articular cartilage as a function of age. Therefore, untreated male SD rats appear to be unsuitable for studying the age-related changes of articular cartilage as they occur in men. However, and more intriguingly, it is also possible that ageing does not affect the biomechanical properties of articular cartilage in the absence of cartilage pathology.

Aging↗

PubMed2000

Electric field-mediated DNA encapsulation into large liposomes.

Large, ethidium bromide-loaded liposomes electrically pulsed in the presence of externally added DNA display the bright fluorescence of DNA-ethidium bromide complexes. Sonication of these liposomes increases the fluorescence of trapped DNA-ethidium bromide complexes by no more than about 40%. These results are thus in agreement with a mechanism involving electropores for DNA uptake but do not support an alternative mechanism, invoking invagination and pinching-off of the lipid bilayer, through which internalized DNA is shielded from the liposome contents.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2000

Knot security in simple sliding knots and its relationship to rotator cuff repair: how secure must the knot be?

We sought to determine which simple sliding knot configurations would have adequate strength for rotator cuff repair. Four knot configurations were tied with both No. 1 polydioxanone suture and No. 2 Ethibond suture (Ethicon, Somerville, NJ) using 3 different tying techniques: hand-tie, standard knot pusher, and cannulated double-diameter knot pusher. The knots were then tested to failure on a materials testing system. The weakest standard knot configuration was S=S=S=S. The other 3 knot configurations (S//S//S//S, SxSxSxS, and S//xS//xS//xS) generally failed in the 35 to 50 N range. Ultimate strength in this range can be shown to be adequate to withstand, without suture failure, a maximal contraction of a repaired rotator cuff tear within the rotator crescent, assuming certain conditions are met (suture anchors placed 1 cm apart, 2 sutures per anchor). More complex knots are not necessary for adequate knot security. However, the same configuration with only 1 suture per anchor will not be strong enough because the suture will fail under maximum physiological load. This study shows that we can predict the adequacy of a given knot configuration under maximum physiological loading conditions.

Arthroscopy↗

PubMed1999

Cytoindentation for obtaining cell biomechanical properties.

A novel biomechanical testing methodology was developed to obtain the intrinsic material properties of an individual cell attached to a rigid substrate. With use of a newly designed cell-indentation apparatus (cytoindenter), displacement-controlled indentation tests were conducted on the surface of individual MG63 cells and the corresponding surface reaction force of each cell was measured. The cells were modeled with a linear elasticity solution of half-space indentation and the linear biphasic theory on the assumption that the viscoelastic behavior of each cell was due to the interaction between the solid cytoskeletal matrix and the cytoplasmic fluid. To obtain the intrinsic material properties (aggregate modulus, Poisson's ratio, and permeability), the data for experimental surface reaction force and deformation were curve-fitted with use of solutions predicted with a linear biphasic finite element code in conjunction with optimization routines. The MG63 osteoblast-like cells had a compressive aggregate modulus of 2.05+/-0.89 kPa, which is two to three orders of magnitude smaller than that of articular cartilage, six to seven orders smaller than that of compact bone, and quite similar to that of leukocytes. The permeability was 1.18+/-0.65 (x10(-10)) m4/N-s, which is four to six orders of magnitude larger than that of cartilage. The Poisson's ratio was 0.37+/-0.03. The intrinsic material properties of the individual cell in this study can be useful in precisely quantifying mechanical stimuli acting on cells. This information is also needed for theories attempting to establish mechanotransductional relationships.

Biomechanical Phenomena↗

PubMed1998

Loop security as a determinant of tissue fixation security.

Secure arthroscopic repair of rotator cuff tears and Bankart lesions requires tight knots (knot security). Equally important, but usually overlooked, is the tightness of the suture loop (loop security). This study compared loop security in knots tied with No. 1 PDS suture using three different methods: (1) hand-tied, (2) single-hole standard knot pusher, and (3) cannulated double-diameter knot pusher. The results of this study show that the double-diameter knot pusher maintained tight suture loops that were equivalent in circumference to hand-tied loops and were significantly tighter than suture loops tied with a standard single-hole knot pusher. This study highlights the fact that loop security is equally important to knot security in tissue fixation.

Arthroscopy↗

PubMed1997

Variations in the mechanical properties of cartilage from the canine scapulohumeral joint.

OBJECTIVE: To measure the intrinsic material properties of scapulohumeral joint cartilage in adult dogs and determine whether regional differences exist within or between the humeral and glenoid cartilages. SAMPLES: Paired shoulder joints from 7 clinically normal adult dogs. PROCEDURE: An automated indentation apparatus was used to obtain the intrinsic mechanical properties of the cartilage at 7 sites on each joint surface. RESULTS: Topographic variations in mechanical properties of the glenoid and humeral cartilages were observed. The largest aggregate modulus (HA) for the humerus was seen at the caudocentral site (0.92 MPa) and for the scapula was seen at the centrocenter site (0.84 MPa). The mean shear modulus (mu) of humeral cartilage (0.23 MPa) was significantly greater than that of the glenoid cartilage (0.19 MPa). The mean Poisson's ratio (v) of humeral cartilage (0.24) was significantly smaller than that for the glenoid cartilage (0.29). Mean humeral cartilage aggregate modulus (0.71 MPa) was larger than the value for glenoid cartilage (0.67 MPa), but these differences were not significant. There were no significant differences in the compressive stiffness of the opposing cartilage in the canine scapulohumeral joint. CONCLUSIONS: Differences in mechanical properties between opposing humeral and glenoid cartilages are not a cause of cartilage injury in the scapulohumeral joint of adult dogs. The mechanical properties of cartilage from young dogs with open physes and incomplete subchondral bone plates may be different from those of adult dogs.

Animals↗

PubMed1996

Comparison of the mechanical performance of trochanteric fixation devices.

The transtrochanteric surgical approach to the hip is commonly used, especially for revision hip surgery. Failure of the trochanter to heal can lead to hardware failure, persistent pain, and limp. Rigid internal fixation is needed in this approach to achieve an adequate rate of healing. Newer cable and cable grip systems have been designed to improve trochanteric fixation, but have not been compared to the older Charnley wire fixation techniques. In this study, an in vitro mechanical method previously used to test wire fixation methods was used to compare wire, cable, and cable grip fixation methods. A quasistatic mechanical distraction device was used to compare structural stiffness, load to clinical failure, energy to clinical failure, and maximum load resisted by the fixation devices. The cable grip system was found to be stiffer, to resist a larger load to mechanical failure at 1-cm displacement, and to absorb a greater amount of energy to clinical failure when compared with the other systems. These data suggest that use of the cable grip fixation method should result in improved clinical success compared with the Charnley wire technique.

Adolescent↗

PubMed1994

Enzymatic synthesis of butyryl-rutin ester in organic solvents and its cytogenetic effects in mammalian cells in culture.

Enzymic acylation of a flavonoid, rutin, with trichloroethylbutyrate (TCEB) has been performed by subtilisin protease in anhydrous pyridine solution. The addition of a hydrophobic compound on rutin is expected to change the hydrophilic/hydrophobic balance of the molecule, giving new properties to this compound. This work aimed at investigating the various cytological properties of the rutin-ester and compared them with those of the native molecule. No difference in the levels of sister chromosomes exchange (SCE) between rutin and rutin-ester treated cells at doses varying from 25 to 200 micrograms/mL was found. On the contrary impressive difference in the induced frequency of micronuclei (MN) between rutin and rutin ester treated cells was observed, for example, at a dose of 100 micrograms/mL of rutin were 3.5% MN counted, whereas for a similar dose treatment with rutin-ester a frequency of 8% of MN was found. The fact that rutin-ester is causing significantly higher levels of MN than the rutin alone can be considered as a manifestation of a higher action of the agent on the chromosome owing to its easier penetration in to the cell after its esterification.

Acylation↗

PubMed1994

Estimating the level of knowledge of Greek students on cancer aetiology and ways of prevention.

The aim of the present research was to establish the perception of the relative importance of various environmental risk factors for cancer among Greek students. A questionnaire was used to assess the students' knowledge on cancer causation. The factors examined included smoking habits, drinking, geophysical factors, pollution, dietary factors, and the students' awareness of the contribution of these factors to the generation of the disease. In addition, we examined the students' attitude to the factors as cancer risk determinants. A random sample of 1,136 students was selected from the matriculated students of various departments of the Aristotelian University of Thessaloniki. We found a relative important lack of knowledge on subjects related to the generation of the disease.

Adolescent↗

PubMed1992

Metsovo-tremolite asbestos fibres: in vitro effects on mutation, chromosome aberration, cell transformation and intercellular communication.

Samples of Metsovo-tremolite asbestos, previously found to be the causative agent of endemic pleural calcification and an increased level of malignant pleural mesothelioma in a rural area of north-western Greece (Metsovo area), were tested in various in vitro toxicity test systems. It was found that asbestos fibres of this type were strong inducers of micronuclei and numerical chromosomal abnormalities while they induced low levels of chromosomal aberrations in mammalian cells in culture. Furthermore, this type of asbestos can induce a low level of in vitro transformation of Syrian hamster embryo cells. The fibres had no effect on gap-junctional cell-cell communication (followed by the dye-transfer method) and did not induce any mutations in the Salmonella typhimurium strain TA102 which is known to be sensitive to the action of various oxidative agents. These results support the hypothesis generated from studies on other types of asbestos that such fibres induce tumours by causing chromosomal mutations.

Aneuploidy↗

PubMed1989

Temperature and time effects on mutagen production in cooked lamb meat.

Basic extracts isolated from lamb meat treated at various temperatures were tested for mutagenicity in Salmonella typhimurium strain TA98 in the presence of S9 mix. Samples of ground lamb patties were cooked for 10 min per side at 100, 150, 200, 250 and 300 degrees C. Low cooking temperatures resulted in products with low levels of mutagenicity. At temperatures greater than 150 degrees C the mutagenic activity of the cooked meat increased to reach a maximum at 300 degrees C. In another series of experiments, lamb patties were cooked at 250 degrees C for 2, 4, 6, 8, 10 and 12 min. Short cooking times (rare products) caused no mutagenic activity and uncooked ground meat showed no activity. Prolonged cooking appeared to increase the mutagenicity of the products with a maximum value at 10 min. The results indicate that the formation of mutagens depends on both cooking temperature and cooking time. The level of mutagenicity tends to increase with the degree of charring.

Animals↗

PubMed1987

Mutagenicity, sister chromatid exchange inducibility and in vitro cell transforming ability of particulates from Athens air.

Airborne particulates were collected over a period of twelve months by the use of Hi-Vol samplers in the basin of Athens, Greece. N-Hexane extracts were tested in a battery of in vitro tests for their ability to induce mutation in bacteria as well as mutation, sister chromatid exchange and morphological transformation in cultured mammalian cells. Positive results were found for mutagenicity with Salmonella strain TA98 in the Ames assay, for sister chromatid exchange induction in CHO cells and for transformation in BALB/c 3T3 cells in culture. They also showed weak non-dose-related induction of ouabain resistance in BALB/c 3T3 cells. The contribution of oxidizing and nitrating agents found in the Athens atmosphere, together with sunlight UV irradiation in the formation of direct acting mutagens and potential carcinogens from ambient polycyclic aromatic hydrocarbons, is suggested.

Air Pollutants↗

PubMed1987

Response of transplantable tumors in mice and of macromolecular synthesis to 17 beta-acetamido-3-aza-A-homo-4 alpha-androsten-4-one.

17 beta-acetamido-3-aza-homo-4 alpha-androsten-4-one has cytostatic activity against Ehrlich ascites tumor, L1210, and P388 leukemias in mice when administered intraperitoneally. The effect of the homo-aza-steroid on the incorporation of radioactive precursors to DNA and RNA of L1210 leukemia cells was investigated. It was found that treatment of cells with 12.5 micrograms/ml of the drug for 1 hour inhibited DNA synthesis by 81%. This was partly because the drug affected the radioactive thymidine pool in the cell. The inhibitory effect was found to be reversable. The incorporation of [3H]thymidine into DNA was lower when cells were incubated in the presence of S9 mix. It was also found that the same compound inhibited RNA synthesis by 67%.

Androstenes↗

PubMed1986

Mutagenicity and polycyclic aromatic hydrocarbons analysis of ambient airborne particles collected in Athens, Greece.

Samples of airborne particulates from the Athens atmosphere were examined for mutagenicity and various polycyclic aromatic hydrocarbons (PAH). Extracts induced linear, dose-related increases in TA98 His+ revertants in the Ames/Salmonella assay and contained average benzo[a]pyrene (BaP) levels of 3.9 ng/m3 of air. The levels of revertants/m3 of the samples showed a linear relation to their BaP and benzo[b]-(BbF) + benzo[k]-fluoranthene (BkF) concentrations and were higher in areas with dense traffic than in industrial areas. It is suggested that the atmosphere of Athens favours the formation of secondary direct-acting mutagens due to the oxidation and nitration of PAH by ozone and nitrogen oxides, which are more abundant in the late spring months.

Air Pollutants↗

PubMed1986

Mutagenicity and clastogenicity of the antineoplastic agents homo-azasteroidal ester of p-bis(2-chloroethyl)aminophenyl acetic acid and chlorambucil.

The mutagenic and clastogenic effects of the antineoplastic agents homo-aza-steroidal ester (ASE) and chlorambucil (CBC) were tested for their ability to induce mutations in the Salmonella/microsome system and SCE in CHO cells in culture. ASE was found to be positive in strains TA1535 and TA100 and in the newer strain TA102 with and without metabolic activation, while CBC caused histidine reversion in strain TA102 after the addition of mammalian liver microsomal extract (S9). In addition, both agents were found to be strongly positive for SCE induction. The mutagenic and clastogenic actions of both agents were of a dose-response type.

Animals↗

PubMed1986

Synthesis of a new nor-aza-steroidal ester of p-N,N-bis-(2-chloroethyl)aminophenylbutyric acid and in vitro study of its mutagenicity and clastogenicity.

A new nor-aza-steroidal ester of chlorambucil has been synthesized. The study of the mitotic index in CHO and HeLa cells treated with this compound showed that it may be a cytostatic drug. It was also found that treatment of CHO cells with a dose as low as 5 micrograms/ml induces a large number of sister chromatid exchanges. A great number of abnormal metaphases has been observed when CHO cells were treated with the compound at a dose of 25 micrograms/ml. When the compound was tested in the Ames/Salmonella microsome assay, it was found to be mutagenic in strains TA100 and TA1535, both with and without metabolic activation.

Animals↗

PubMed1983

Chromosome damage and SCE induced by the cytostatic factor homo-aza-steroidal ester of P-bis (2-chloro-ethyl) amino phenyl acetic acid in CHO cells in culture.

The cytogenetic effects of homo-aza-steroidal ester (ASE) on Chinese hamster ovary (CHO) cells in vitro are reported. It was found that treatment of cells with a dose as low as 0.025 micrograms/ml of ASE causes a significant number of abnormal metaphases containing mostly chromatid-type aberrations. Similarly, significant frequencies of SCE were induced with only 0.075 micrograms/ml of ASE.

Animals↗

PubMed1983

Mutagenic and clastogenic effects of organic extracts from the Athenian drinking water.

Organic extracts of chlorinated drinking water collected from the water distribution system of Athens, Greece, were tested in parallel for their ability to cause mutations in the Salmonella His+ reversion system and sister chromatid exchanges (SCE) and chromosomal aberrations in CHO cells. They were found to induce His+ revertants in frequencies similar to those detected previously with drinking water extracts from other areas around the world. We observe that organic samples from surface drinking water induce SCE and chromatid type abnormalities in CHO cell cultures while samples collected from ground drinking water did not. These findings confirm that chlorinated surface drinking water contains substances which are mutagenic and clastogenic and may be carcinogenic in humans.

Animals↗