[Determination of a Friction Coefficient for THA Bearing Couples]. / Stanovení soucinitele trení hlavic a jamek TEP kycle.

PURPOSE OF THE STUDY: The wear of articular surfaces is considered one of the most important factors limiting the life of total hip arthroplasty (THA). It is assumed that the particles released from the surface of a softer material induce a complex inflammatory response, which will eventually result in osteolysis and aseptic loosening. Implant wear is related to a friction coefficient which depends on combination of the materials used, roughness of the articulating surfaces, internal clearance, and dimensions of the prosthesis. MATERIAL AND METHODS: The selected parameters of the bearing couples tested were studied using an experimental device based on the principle of a pendulum. Bovine serum was used as a lubricant and the load corresponded to a human body mass of 75 kg. The friction coefficient was derived from a curve of slowdown of pendulum oscillations. Roughness was measured with a device working on the principle of interferometry. Clearance was assessed by measuring diameters of the acetabular and femoral heads with a 3D optical scanner. The specimens tested included unused metal-on-highly cross-linked polyethylene, ceramic-on-highly cross-linked polyethylene and ceramic-on-ceramic bearing couples with the diameters of 28 mm and 36 mm. For each measured parameter, an arithmetic mean was calculated from 10 measurements. RESULTS: 1) The roughness of polyethylene surfaces was higher by about one order of magnitude than the roughness of metal and ceramic components. The Protasul metal head had the least rough surface (0.003 µm). 2) The ceramic-on-ceramic couples had the lowest clearance. Bearing couples with polyethylene acetabular liners had markedly higher clearances ranging from 150 µm to 545 µm. A clearance increased with large femoral heads (up to 4-fold in one of the couple tested). 3) The friction coefficient was related to the combination of materials; it was lowest in ceramic-on-ceramic surfaces (0.11 to 0.12) and then in ceramic-on-polyethylene implants (0.13 to 0.14). The friction coefficient is supposed to increase with a decreasing femoral head diameter. However, in the bearing couples with polyethylene liners manufactured by one company, paradoxically, the friction coefficient slightly increased with an increase in femoral head size from 28 mm to 36 mm. 4) The lowest friction moment (< 3.5 Nm) was found for ceramic-on-ceramic implants 28 mm in diameter; the highest values were recorded in metal-on-polyethylene bearing couples 36 mm in diameter (> 7 Nm). DISCUSSION: Although our study confirmed that the bearing couples produced by different manufacturers varied to some extent in the parameters studied, in our opinion, this variability was not significant because it was not within an order of magnitude in any of the tests. CONCLUSIONS: The study showed that both the friction coefficient and the friction moment are affected more by the combination of materials than by the diameter of a femoral head. The best results were achieved in ceramic-on-ceramic implants.

Cytomembrane-derived Birbeck granules transport horseradish peroxidase to the endosomal compartment in the human Langerhans cells.

It has been previously shown that the cytomembrane of human Langerhans cells (LC) has the capacity to fold upon itself, thereby forming Birbeck granules (BG), which then internalize. I confirmed this by exposing LC in vitro to horseradish peroxidase (HRP) at +8 degrees C and +37 degrees C. On incubation at +37 degrees C the label appeared not only in BG, but also in tubular structures and vesicles of different shapes and sizes. Interconnections between these labeled endosomal structures were common. The LC cytomembrane could form BG at +8 degrees C and, moreover, the BG was the only organelle that was labeled and internalized at this temperature. Thus, cytomembrane-derived BG are endocytotic in nature and link the exterior of the cell and the endosomal compartment. The membrane interlinking of the BG may eventually dissolve and the BG then transform into an endosomal vesicle.

Melanin and melanosome complexes in long standing stable vitiligo--an ultrastructural study.

To investigate the presence of melanin and melanocytes (MC) in stable vitiligo, skin biopsies from five patients with vitiligo lesions of between 1 to 17 years duration were examined under the electron microscope. Areas of the upper dermis and epidermis were explored. There was a significant amount of melanin in a few keratinocytes (KC) grouped in the stratum basale in 1-3 year-old vitiligo lesions. In these KC, the melanosomes were most often aggregated into melanosome complexes (MCo) while the remaining KC were completely devoid of melanin. Solitary MCo were also observed in a few dermal cells in all vitiligo biopsies. All non-keratinocytes were scrutinized in series of 200-300 consecutive sections and were identified according to morphological characteristics. Neither active nor inactive MC, nor MC dendrites were found. These observations show that melanin in non-negligible amounts can be found even in 3 year-old vitiligo epidermis. Since there were no MC detected in the epidermis it implies that the melanosomes can persist in certain KC for some time after the onset of vitiligo.

Elastic fibers in dermis of juvenile elastoma.

To explore the ultrastructure of elastic fibers in juvenile elastoma, three patients (two without osteopoikilosis and one under examination of bones and joints) were studied by routine electron microscopy. In addition to normal elastic fibers, all the patients also exhibited alterations in elastic fibers. The altered ultrastructures showed lucent, homogenous matrix without peripheral microfibrils. The homogenous matrix were seen in various extensions from the small protrusions of the normal elastic fibers to the complete replacement of the entire fibers. Collagen fibrils occasionally showed twisted figures. Normal shapes of dermal glycosaminoglycans were increased in number. It seems likely that the lucent, homogenous matrix without peripheral microfibrils are the characteristic changes of elastic fibers in juvenile elastoma. The alteration could be nevoid in nature.

Melanosome complexes and melanin macroglobules in normal human skin.

The presence of melanin macroglobules, and sometimes that of melanosome complexes also, in epidermal melanocytes has been considered a feature of various skin diseases. Opinions differ as to whether these structures can occur in normal skin. We have studied these melanin inclusions in normal Caucasian skin in the entire soma of 116 melanocytes and the occurrence of melanosomes in phagosomes of 77 Langerhans' cells obtained in different seasons. During winter the melanocytes contained few melanosomes but many melanosome complexes and melanin macroglobules. These melanosome inclusions were in 86%, localized in the most basal part of the melanocytes, particularly in the dermal protrusions. It is suggested that these structures can be transferred from epidermal melanocytes to dermal cells and that melanin macroglobules derive from melanosome complexes. Irrespective of the season, most of the Langerhans' cells contained melanosomes in their phagosomes, which suggests a phagocytic capacity of these cells and a role in the elimination of the melanin.

Systemic ketoconazole for yeast allergic patients with atopic dermatitis.

BACKGROUND: Adult patients with atopic dermatitis (AD), especially with the head-neck distribution, are often sensitized to the lipophilic yeast Malassezia furfur/Pityrosporum orbiculare, which is considered to contribute to the pathogenesis of the dermatitis. OBJECTIVE: Evaluation of the efficacy of oral ketoconazole on immunological and clinical parameters in yeast allergic adult patients with AD. STUDY DESIGN: Randomized double-blind placebo-controlled study. SUBJECTS: Twenty-nine patients with specific IgE antibodies to M. furfur/P. orbiculare and with elevated serum IgE participated in the investigation. Fifteen subjects were treated with 200 mg ketoconazole daily and 14 received placebo for 3 months. Betamethasone cream was allowed as supplementary therapy and the consumption was registered. The clinical score (SCORAD), total serum IgE and specific IgE antibodies to M. furfur/P. orbiculare, Candida albicans and Dermatophagoides pteronyssinus were monitored at the starting point and by the end of the first and third month. RESULTS: In the actively treated group the levels of specific IgE to M. furfur/P. orbiculare and C. albicans as well as total serum IgE decreased significantly. Sensitization to D. pteronyssinus was not influenced. The clinical score decreased in both groups, and the improvement was correlated to the consumption of topical steroids in the control group but not in the ketoconazole group.

Human epidermal Langerhans' cells are sensitive to rapid cooling by ethyl chloride.

Topical anesthesia with ethyl chloride spraying generates some remarkable reactive events in the human Langerhans' cell (LC) system. Many LC retract their dendrites and a considerable number move to the innermost layers of the epidermis within 15 minutes. This rapid motility supports the view that the interstices between cells in living epidermis are large. The LC cytomembrane is very susceptible to cold shock which causes the cytomembrane to superimpose upon itself forming abnormally shaped Birbeck granules. This process may consume too much of the cytomembrane to be compatible with cell survival.

Cytomembrane-sandwiching in human epidermal Langerhans cells: a novel reaction to an irritant.

Relatively mild exposure of human epidermis to sodium lauryl sulphate caused a general activation of the Langerhans cell system within 5 hours. An unexpected reactive phenomenon was that this irritant caused some cytomembrane parts to fold upon each other, thereby forming numerous Birbeck granules, several of which had an irregular shape. Spotty cytomembrane damage to the Langerhans cells was also observed.

Quantification of Birbeck's granules in human Langerhans' cells.

A proper understanding of the function of Birbeck's granules requires that they should be counted under various conditions. We now present a simple quantification method which does not depend on specific assumptions concerning size, shape or location of the particles counted and can, moreover, be applied for counting other subcellular structures as well. A population of 69 serially sectioned human Langerhans' cells had an average of 290 granules and no cell contained fewer than 96 granules, indicating that as they degrade, granules are continuously formed. Suprabasal Langerhans' cells contained significantly more granules than did the basal cells.

Direct evidence for the cytomembrane derivation of Birbeck granules: the membrane-sandwich effect.

Digitonin, which is known to cause extensive damage to cytomembranes in general, was found to have a most remarkable effect on epidermal Langerhans' cells. Thus, it generates a membrane-sandwiching process resulting in the formation of large discs which except for the differences in size have the same morphology as ordinary Birbeck granules. This demonstrates that the cytomembrane of the Langerhans' cell has the inherent ability to superimpose upon itself, leaving little doubt that the normal Birbeck granules derive from the cytomembrane.

Variable expression of apoptotic phenotype in keratinocytes treated with ultraviolet radiation, ceramide, or suspended in semisolid methylcellulose.

Apoptosis is a form of cellular suicide and is activated in various cells, including keratinocytes, in response to physiological and pathological stimuli. A current hypothesis holds that apoptotic cells in a concerted manner express characteristic phenotypic features comprising cytoplasmic budding, pyknosis, chromatin condensation, karyorhexis and internucleosomal DNA fragmentation. In this study we investigated the effects of different potential inducers of apoptosis on cultured human keratinocytes. Viability was determined with vital dyes (ethidium bromide, trypan blue), cell morphology was investigated with electron microscopy, and nuclear and DNA integrity was assessed with TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling) or DNA gel electrophoresis. Irradiation with 50 mJ/cm2 ultraviolet B (UVB), treatment with C8 ceramide, or suspension in a semisolid medium caused apoptosis which was ultrastructurally different from necrotic induced by very high (300 mJ/cm2) doses of UVB. However, the phenotype of dying cells did not exhibit all typical features of apoptosis and cell morphology depended on the method used to induce apoptosis. Cells irradiated with ultraviolet B or treated with C8 ceramide developed large and small budding and DNA nicks but not chromatin condensation or classical karyorhexis. In UVB-irradiated cells a novel form of karyorhexis was observed manifested by formation of a few very small chromatin fragments in nuclear periphery. Cells suspended in methylcellulose developed DNA nicks and pyknosis, but not budding or karyorhexis. In neither case could the typical internucleosomal DNA fragments be detected by gel electrophoresis. These morphological results indicate that in keratinocytes induction of effect or death mechanisms is not concerted but depends on the stimulus inducing apoptosis.

Reconstruction of the standard 12-lead ECG from recordings using nonstandard activity-compatible proximal limb lead positions.

Proximal or torso placement of limb leads in the 12-lead electrocardiogram (ECG) has been shown to influence the appearance of QRS waveforms considerably. A method was developed for computer-based reconstruction of standard-like waveforms from nonstandard torso-recorded waveforms. Reconstruction coefficients required by the method were determined using ECG data obtained from 30 patients. The coefficients were then applied on an independent test set of 100 patients. In 21 of these patients, a second standard EGG was obtained the next day to determine the day-to-day variation in QRS waveforms. R wave amplitudes in leads I and II, and electrical axes in the frontal plane were measured in the standard ECG, the nonstandard ECG, and the reconstructed ECG. It is shown that the reconstruction method yields ECGs that differ less from standard than do two standard ECGs recorded on consecutive days. The performance of the reconstruction method was not influenced by age, sex, height, or weight.

Bone mineral density in patients with Crohn's disease during long-term treatment with azathioprine.

OBJECTIVES: To ascertain whether patients with Crohn's disease treated with azathioprine maintained bone mineral mass better than patients treated with steroids alone. DESIGN: Retrospective study. SETTING: University Hospital of Malmö, Sweden. SUBJECTS: A total of 59 patients with ileocolonic, ileocaecal or colonic Crohn's disease. METHODS: Bone mass was assessed by dual photon X-ray absorptiometry at the level of L2-L4. RESULTS: Patients treated with a high lifetime dose of steroids (> 5 g prednisolone) had significantly (P = 0.011) lower Z-score of L2-L4 (-0.87 +/- 1.11; 11 SD) than steroid-treated patients, who had received a low dose of prednisolone (< 5 g) (0.08 +/- 1.16 SD). Azathioprine did not negatively influence the steroid effect on bone mineral density. CONCLUSIONS: Azathioprine does not seem to affect bone mineral density by itself. However, by being steroid-saving, it seems to conserve bone mineral mass in patients with Crohn's disease.

Atopy patch test reactions to Malassezia allergens differentiate subgroups of atopic dermatitis patients.

BACKGROUND: The yeast Malassezia is considered to be one of the factors that can contribute to atopic dermatitis (AD). OBJECTIVES: To investigate the reactivity to Malassezia allergens, measured as specific serum IgE, positive skin prick test and positive atopy patch test (APT), in adult patients with AD. METHODS: In total, 132 adult patients with AD, 14 with seborrhoeic dermatitis (SD) and 33 healthy controls were investigated for their reactions to M. sympodialis extract and three recombinant Malassezia allergens (rMal s 1, rMal s 5 and rMal s 6). RESULTS: Sixty-seven per cent of the AD patients, but only one of the SD patients and none of the healthy controls, showed a positive reaction to at least one of the Malassezia allergens (extract and/or recombinant allergens) in at least one of the tests. The levels of M. sympodialis-specific IgE in serum correlated with the total serum IgE levels. Elevated serum levels of M. sympodialis-specific IgE were found in 55% and positive APT reactions in 41% of the AD patients with head and neck dermatitis. A relatively high proportion of patients without head and neck dermatitis and patients with low total serum IgE levels had a positive APT for M. sympodialis, despite lower proportions of individuals with M. sympodialis-specific IgE among these groups of patients. CONCLUSIONS: These results support that Malassezia can play a role in eliciting and maintaining eczema in patients with AD. The addition of an APT to the test battery used in this study reveals a previously overlooked impact of Malassezia hypersensitivity in certain subgroups of AD patients.