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Tissue-engineering approaches for cartilage repair hold promise for the treatment of cartilage defects. Various methods to prevent or reduce dedifferentiation during chondrocyte expansion are currently under investigation. In the present study we evaluated the effect of oxygen on chondrocyte proliferation, as oxygen has received increased attention as a possible regulator of chondrocyte differentiation and its effect during expansion is uncertain. Therefore, the effect of three oxygen tensions (4, 10.5, and 21%) was investigated in a bioreactor microcarrier culture, which allows precise control of the oxygen tension in the liquid phase. During culture cells acquired a round shape on microcarriers. No differences in proliferation rate of chondrocytes were observed within the range of oxygen tensions evaluated. Cells exhibited predominantly anaerobic metabolism and, per mole of glucose, approximately 2 mol of lactate was produced independent of oxygen tension. Cellular oxygen consumption was comparable for all bioreactor cultures. Nevertheless, specific consumption rates were relatively high (2-4 x 10(-17) mol. cell(-1). s(-1)), in comparison with chondrocytes in cartilage (0.8-2.2 x 10(-18) mol. cell(-1)). Subsequent cartilaginous tissue formation in pellets was not affected as qualitatively assessed by safranin-O staining. At the oxygen concentrations evaluated, no effect of oxygen tension was observed on proliferation, oxygen consumption, and yield of lactate on glucose administration. For future investigations of chondrocytes and oxygen, the bioreactor system, which allows precise control and monitoring of oxygen tension, holds promise.

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Functional cartilage implants for orthopedic surgery or in vitro tissue evaluation can be created from expanded chondrocytes and biodegradable scaffolds. Expansion of chondrocytes in two-dimensional culture systems results in their dedifferentiation. The hallmark of this process is the switch of collagen synthesis from type II to type I. The aim of this study was to evaluate the postexpansion chondrogenic potential of microcarrier-expanded bovine articular chondrocytes in pellet cultures. A selection of microcarriers was screened for initial attachment of chondrocytes. On the basis of those results and additional selection criteria related to clinical application, Cytodex-1 microcarriers were selected for further investigation. Comparable doubling times were obtained in T-flask and microcarrier cultures. During propagation on Cytodex-1 microcarriers, cells acquired a spherical-like morphology and the presence of collagen type II was detected. Both observations are indicative of a differentiated chondrocyte. Pellet cultures of microcarrier-expanded cells showed cartilage-like morphology and staining for proteoglycans and collagen type II after 14 days. In contrast, pellets of T-flask-expanded cells had a fibrous appearance and showed abundant staining only for collagen type I. Therefore, culture of chondrocytes on microcarriers may offer useful and cost-effective cell expansion opportunities in the field of cartilage tissue engineering.

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A substantial increase in [125I]Sar1, Ile-Angiotensin II binding activity can be observed 24 hours after treatment of R3T3 cells with AT2 receptor agonists and antagonists. An increase in the radioligand binding activity, although less profound, can also be observed 6 hours after AT2 receptor ligand treatment, on fetal human kidney cells expressing a recombinant human AT2 receptor. However, the increase in radioligand binding activity cannot be detected unless the ligands are removed from the cell surface by an acid-glycine (pH 3) wash, just prior to the binding assay. Interestingly, an acid-glycine wash 24 hours prior to the binding assay causes a dramatic decrease in the radioligand binding activity on untreated R3T3 cells. This decrease, which was prevented by angiotensin II treatment, suggests the existence of an unknown endogenous factor which, like the AT2 receptor ligands, seems to prevent AT2 receptor degradation.

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The fatty acid composition of total lipids and the adrenoceptor-mediated activation of glycogenolysis were studied in isolated hepatocytes from rats maintained on a control diet or on an essential fatty acid (EFA)-free diet. In cells from rats on the EFA-free diet there was a marked reduction in linoleic and arachidonic acid (AA) contents and an increase in eicosatrienoic, oleic, and palmitoleic acid contents compared to controls. In freshly isolated cells from both groups, phosphorylase a activity was increased by phenylephrine or epinephrine but not by isoproterenol, and the effect of epinephrine was inhibited by phenoxybenzamine but not by propranolol. When control cells were preincubated in a serum-free buffer for 4 h before testing, the effect of phenylephrine on phosphorylase a activity was reduced, isoproterenol became a potent agonist and the effect of epinephrine was partially inhibited either by phenoxybenzamine or by propranolol. The emerging beta-adrenergic response in 4-h cells was associated with a marked potentiation of isoproterenol-induced cAMP accumulation. A similar 4-h preincubation of EFA-deficient cells resulted in a reduced response to phenylephrine while isoproterenol remained ineffective for increasing either phosphorylase a activity or cAMP production. The response of these 4-h cells to isoproterenol could be restored by in vivo replacement of the EFA-deficient diet with control diet for the last 4 weeks prior to the experiment, but not by the in vitro exposure of the EFA-deficient cells to 10 microM AA throughout the 4-h incubation period. Extending previous observations (Refs. (6-8)), the present results suggest that the time-dependent emergence of beta-adrenergic glycogenolysis, but not the parallel reduction of the alpha-adrenergic response, is mediated by AA or its metabolite(s), which probably act by facilitating the G-protein-dependent coupling of beta-receptors.

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Plasma fatty acids contents and dynamics of the left cardiac ventricle contractions were determined in 48 children with simple obesity. Significant deterioration of the dynamics of left ventricle contractions was seen in obese children. It included prolongation of QSIIJ, QI, and PEPI and shortening of LVETI. Correlation of the total contraction time, pre-ejection period and contractility index with plasma saturated and unsaturated fatty acids levels has been demonstrated.

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Percent composition of the plasma fatty acids in 48 children with simple obesity was determined with gas-chromatography. Thirty seven healthy, normotensive children served as the control group. An increased content of the saturated fatty acids and decreased content of the unsaturated fatty acids together with the decrease in unsaturated fatty acids:multi-unsaturated fatty acids ratio were seen in children with simple obesity.

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The studied group comprised 82 children with simple obesity. In the group the character and frequency of ECG changes in 12 conventional leads were analyzed. A correlation was established between the character and frequency of these changes and the degree of overweight and obesity duration. In children with simple obesity a considerable prevalence was observed of disturbances of sinus rhythm, impairment of intraventricular conduction and signs of left ventricular hypertrophy. The observed changes were more frequent in children with over 5 years of obesity duration. No correlation was demonstrated between the incidence of these changes and the degree of overweight.

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During 10 minutes of infusion of noradrenaline in doses of 0.1, 0.2, 0.4 and 0.6 micrograms/min into isolated intestinal, kidney and hindquartet preparation, perfused with aerated Tyrode's solution and escape effect was observed in normotensive rats. The escape was significantly reduced in intestinal and renal vascular beds or disappeared in spontaneously hypertensive rats.

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The content of certain fatty acids of the serum and erythrocytes was compared in rabbits before and after 11 days on a diet with added cholesterol. The alimentary cholesterol load reduced the levels of linolic and arachidonic acids in the serum, while in the erythrocytes the level of linolic acid was increased. Changes in the levels of the remaining determined fatty acids were not significant statistically.

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In 81 children aged 0-18 years with normal body weight the serum pattern of fatty acids (FA) were determined by means of gas chromatography. The results show that of the 11 FA determined chromatographically, unsaturated and saturated fatty acids had differences in their distribution in the plasma. A certain regularity of these differences in favour of unsaturated fatty acids was observed. At the same time it was demonstrated that the mean values of unsaturated essential fatty acids (EUFA) increased with the age of a child. These results suggest that the plasma FA pattern may be a valuable supplementary source of information about lipid metabolism disturbances in children.

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The levels of serum fatty acids in the serum and in the serum fractions of cholesterol esters (ECH) and triglycerides (TG) and the levels of these acids in these fractions of platelets were compared in healthy controls and in patients with clinically manifested coronary arterial disease. Decreased level of linoleic acid was found in the serum and in the ECH fraction of the serum in the patients, with a rise in the level of palmitic acid in the ECH fraction of the serum of these patients. The level of linoleic acid in the ECH and TG platelet fractions in these patients was not different from that in the healthy controls, while in the platelet TG fraction of the patients the level of palmitoleic acid was raised, and the level of oleic acid was increased in the platelet ECH fraction.

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Minimal physical activity was used as a preliminary procedure before measuring some physiological parameters at rest. Minimal activity preceding the analyzed rest period causes a decrease in the mean heart rate (by 5.4%), respiratory rate (by 3.5%), O2 uptake (by 2.5%) and respiratory quotient in parallel determinations in the same individuals reducing particularly the standard deviations of mean values. These changes are similar to those found after prolonged training.

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