A molecular theory of cartilage viscoelasticity

Recent work on the subject of cartilage mechanics has begun to focus on the relationship between the microscopic structure of cartilage and its macroscopic mechanical properties (Bader et al., Biochem. Biophys. Acta, 1116 (1992) 147-154; Buschmann, PhD Thesis, Massachusetts Institute of Technology, 1992; Kovach, Biophys. Chem., 53 (1995) 181-187; Lai et al., J. Biochem. Eng., 113 (1991) 245-248; Armstrong and Mow, J. Bone Jt. Surg., 64A (1982) 88; Jackson and James, Biorheology, 19 (1982) 317-330). This paper reviews recent theoretical developments and presents a comprehensive explanation of the viscoelastic properties of cartilage in terms of molecular structure. In doing this, a closed form hybrid solution to the non-linear, cylindrical Poisson-Boltzmann equation is developed to describe the charge-dependent component of the equilibrium elasticity arising from polysaccharide charge (Benham, J. Chem. Phys., 79 (4) (1983) 1969-1973; Einevoll and Hemmer, J. Phys. Chem., 89 (1) (1988) 474-484; Fixman, J. Chem. Phys., 70 (11) (1979) 4995-5001; Ramanathan and Woodburg, J. Chem. Phys., 82 (3) (1985) 1482-1491; Wennerstrom et al., J. Chem. Phys., 76 (9) (1982) 4665-4670). This solution agrees with numerical solutions found in the literature (Buschmann, PhD Thesis, Massachusetts Institute of Technology, 1992). The charge-independent, entropic contribution to the equilibrium elasticity is explained in a manner similar to that recently presented for concentrated proteoglycan solution (Kovach, Biophys. Chem., 53 (1995) 181-187). This approach exploits a lattice model of the solution, subject to a Bragg-Williams type approximation to derive the volume dependence of polysaccharide configuration entropy (Flory, Principles of Polymer Chemistry, Cornell University Press, Ithaca, NY, 1953; Huggins, Some properties of Solutions of Long-chain Compounds, 1941, pp. 151-157; Stanley, Introduction to Phase Transitions and Critical Phenomena, Oxford University Press, Oxford, 1971). Together, these two contributions accurately reproduce the experimentally determined osmotic pressure of cartilage as previously determined by Maroudas (Maroudas and Bannon, Biorheology, 18 (1981) 619-632). The time-dependent, or creep, phenomena which cartilage exhibits when subject to mechanical load is explained in terms of frictional drag on the polysaccharide chain monomers in terms of a Kirkwood-Riseman type model (Kirkwood and Riseman, J. Chem. Phys., 16 (6) (1948) 573-579). This approach is shown to accurately predict the hydraulic permeability of cartilage as previously determined by Maroudas (Madouras, Ann. Rheum. Dis., 34 (suppl. 3) (1975) 77). By use of a quasi-static approximation (neglecting inertial effects) the time-dependent response to a uniform compressive force is determined and also found to be in good agreement with experimental values from the literature.     

Intestinal leakage of technetium-99m-MDP in primary intestinal lymphangiectasia

We present a case in which a patient with primary intestinal lymphangiectasia demonstrated abnormal intestinal accumulation of tracer during 99mTc-methylene diphosphonate (MDP) skeletal scintigraphy. Early intestinal leakage with gradual colonic migration and concentration was confirmed by repeat bone scan with serial acquisitions. The mechanism for the intestinal localization of 99mTc-MDP seen in this patient is not clear. Thus, intestinal lymphangiectasia can be a cause for extra-osseous localization of bone scan agents in the intestine.     

Chronobiologic aspects of ischemic coronary artery disease

Convincing evidence is now available suggesting that several unfavorable cardiovascular events respect a well-defined diurnal pattern in their occurrence. In particular, ischemic heart disease has been widely investigated, and many data indicate a constellation of underlying risk factors whose temporal coincidence might act as triggering factors in the occurrence of acute events. In this paper, the recent knowledge concerning both epidemiology of ischemic heart disease and potentially favoring factors are reviewed from a chronobiological point of view.     

Complete clinical remission and subsequent relapse of bronchiectasis-related (AA) amyloid induced nephrotic syndrome

Systemic amyloidosis normally has a dismal prognosis. However, there are several case reports of protracted survival, usually as a response to measures designed to retard the further deposition of amyloid fibrils. In AA amyloid, most commonly associated with inflammatory rheumatological, bowel, and chest diseases, such interventions have had some success, but the dramatic response of complete resolution of nephrotic syndrome as a result of the regular institution of postural chest drainage and antibiotic therapy, in the clinical context of bronchiectasis, has been previously reported only once. In both of our cases, after protracted remission, such therapy was abandoned by the patients, leading both to recurrence of nephrotic syndrome and also eventually to end-stage renal failure requiring dialysis.     

The evaluation of the cytotoxicity of preparations with anticarcinogenic action in human cell cultures

An approach for determination of cytotoxicity of chemical and biological drugs which combine the estimation of quality and quantity of cells after their treatment are proposed by the authors. The visual control of cellular minicultures permits one: 1) to register specific and pathologic alterations of cell morphology, 2) to trace their development in dynamics under the action of individual or complex drugs and 3) to choose the optimum time for the experiment fixation. The special staining of the treated cells and measurement of the optical density of absorbed histological dye permits one to make a conclusion about the changing of the cells quantity. A combined method of double estimation gives the opportunity to detect the artefacts taking place after staining the cells treated by some drugs and extracts of natural origin in high concentrations.     

Clinical aspects and diagnostic characteristics of nontraumatic intracerebral hemorrhage

The results of treatment of 235 young and middle age patients with nontraumatic intracerebral haemorrhage were analyzed. Diagnosis was verified with the help of computer tomography, magnetic-resonance tomography, angiography and basing on operational and autopsy data as well. Three main symptoms, reflecting the dislocational changes dynamics, were assigned.     

Expression of the opioid growth factor, [Met5]-enkephalin, and the zeta opioid receptor in head and neck squamous cell carcinoma

Heterogeneity of DNA content in multiple hepatocellular carcinomas (HCCs) was investigated by flow cytometry in 62 tumours from 26 patients who had undergone surgical treatment for multiple synchronous HCCs. Heterogeneity of DNA content was defined (a) when tumours had a different DNA ploidy pattern or (b) when the difference in the DNA index of the aneuploid clone was more than 0.1. A tumour with DNA aneuploidy was observed in 17 (66%) of the 26 patients. Heterogeneity of the DNA content was demonstrated in 12 (46%) out of 26 patients: in ten cases by definition (a) and in two cases by definition (b). Histological examination revealed that, of the 12 patients with a heterogeneous tumour DNA content, seven (58%) had a heterogeneous and the remaining five (42%) had a homogeneous type and grade of differentiation among the tumours, showing the absence of a relationship between histological heterogeneity and DNA content. The present results suggest the clinical relevance of DNA content analysis for identifying the clonal origin of multiple HCCs.