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Biomedical subjects

K Madsen

Publications and source records attributed to K Madsen.

At least 73 records · Page 4Linked to original sources
PubMed1988

Stimulation of chondrocyte DNA synthesis by interleukin-1.

Interleukin-1 (IL-1)-containing conditioned media (CM) from activated guinea-pig peritoneal macrophages were found to stimulate the DNA synthesis of rat epiphyseal chondrocytes in vitro. Sephadex G 150 chromatography revealed that the chondrocyte-stimulating activity was molecularly heterogeneous, with apparent molecular ratios of 16,000-21,000 (16-21K), 45-50K, 80-90K, and more than 100K. The IL-1 activity, as estimated by a murine thymocyte activation assay, co-eluted with the 16-21K chondrocyte-stimulating peak, indicating that IL-1 might stimulate the DNA synthesis of chondrocytes in vitro. This assumption was verified in experiments demonstrating a dose-dependent stimulation of chondrocyte DNA synthesis by recombinant human IL-1 alpha. CM from resting and proliferating chondrocytes lacked detectable IL-1 activity, speaking against an autocrine role of IL-1 in epiphyseal cartilage growth. The results suggest that IL-1, in addition to its other effects in inflammatory responses, also acts as a chondrocyte growth factor. This might be one mechanism behind the reactive formation of cartilage in inflamed joints and the increased longitudinal bone growth often seen in affected limbs of children with arthritis.

Animals↗
PubMed1988

The treatment of isovaleric acidemia with glycine supplement.

Although dietary leucine restriction and supplemental glycine are used to treat patients with isovaleric acidemia [deficient isovaleryl-CoA-dehydrogenase (E.C.1.3.99.10)], little quantitative information is available regarding their optimum relationship. Herein we compare different glycine supplements and quantitate isovalerylglycine produced in two patients with clinically different forms of isovaleric acidemia during restricted leucine intake and during oral leucine loading. We found that under stable conditions of leucine restriction, 150 mg glycine/kg/day is an optimum glycine supplement and that glycine supplements of more than 250 mg/kg/day may result in reduced isovalerylglycine production; that when isovaleric acid accumulation is increased, glycine supplements to 600 mg/kg/day will increase isovalerylglycine production; and that the phenotype of isovaleric acidemia is related not only to the extent of impaired isovaleryl-CoA dehydrogenase, but also the ability to detoxify accumulated isovaleryl CoA to isovalerylglycine.

Carbon Dioxide↗
PubMed1988

Relation between energy expenditure and body composition in man: specific energy expenditure in vivo of fat and fat-free tissue.

The relationship between energy expenditure and body composition, in terms of fat and fat-free masses, has previously been described by a variety of predictive regression equations with parameters devoid of physiological content. We present here results obtained by calculating the specific energy expenditure, ie, the energy expenditure per unit of mass, of fat and fat-free tissue on the basis of measurements of the total energy expenditure (EE), the masses of fat (FM), and fat-free (FFM) tissue using the following simple model: EE = k1.FM + k2.FFM where k1 and k2 are the specific energy expenditures of fat and fat-free tissue, respectively. The results of observations on 104 women at rest yielded values for k1 and k2 of 0.31 and 1.35 watts/kg of fat and fat-free mass, respectively, with standard errors of estimate of 0.074 and 0.052 watts/kg, respectively. Analysis of several series of measurements, from other sources and on smaller samples of subjects, yielded similar values at rest but with larger standard errors of estimate. Data from subjects performing varying amounts of work in 24-h measurements showed, as expected, larger values for both tissues. The results explain to a very large extent the well-established relation between resting metabolic rate and body weight, ie, a linear relation with a non-zero intercept. The results also offer a clear-cut explanation for the well known difference in energy expenditure between men and women with the same body weight.

Adipose Tissue↗
PubMed1987

The influence of indomethacin on biomechanical and biochemical properties of the plantaris longus tendon in the rabbit.

It has previously been reported that indomethacin inhibits fracture healing and heterotopic bone formation. Stimulated by these reports, we undertook the present investigation to study the influence of indomethacin on biomechanical and biochemical properties of the plantaris longus tendon in the rabbit. Sixty-eight New Zealand White rabbits were used for the experiment. Half of them were treated with indomethacin, 10 mg/kg orally a day, and the other half with placebo. After 4, 8, and 16 weeks of treatment biomechanical and biochemical variables were determined and compared between the two groups. After 16 weeks there was a significant increase in tensile strength in the group treated with indomethacin. There was no certain concomitant change in the total collagen content, the amounts of soluble and insoluble collagen, or the water content. Further investigations concerning the influence of indomethacin on tendon healing are indicated.

Animals↗
PubMed1987

Subcellular location of IGF-I in chondrocytes from rat rib growth plate.

Ultrathin cryosections of segments of growth plates from rat rib and isolated, gelatin-embedded chondrocytes from the same source were used to demonstrate the ultrastructural location of IGF-I in the different layers of the growth plate. Sections were incubated with a polyclonal rabbit antiserum to free IGF-I and colloidal gold coated with goat anti-rabbit IgGs. The gold label was present in all chondrocytes, localized almost exclusively to the cytoplasm. Particularly the cells in the proliferating zone displayed considerable amounts of gold label. In these cells, gold label was predominantly present over the rough endoplasmic reticulum and membrane bound vesicles, with only negligible gold label over the nuclei and cartilage matrix. The distribution of gold label in the chondrocytes from the proliferating zone, especially in the rough endoplasmic reticulum, strongly suggests that IGF-I can be synthesized by these cells. However, further studies are needed to verify whether there is a local synthesis of IGF-I in the chondrocytes and whether it is under control of growth hormone.

Animals↗
PubMed1987

Stimulative effect of somatostatin on cell proliferation in cultured chondrocytes.

We have earlier demonstrated that human growth hormone stimulates DNA synthesis and proteoglycan production in cultured chondrocytes. The present study is concerned with the effects of somatostatin and other neuropeptides on cell proliferation by cultured rat rib growth plate chondrocytes. Chondrocytes were isolated from the growth plates by collagenase digestion and cultured as monolayers in multiwell plates. The cells were allowed to attach overnight and subsequently incubated for 24 h under serum-free conditions to establish growth arrest. Somatostatin and other peptides were then added and the cultures were incubated for 18 h. Finally, the cultures were labelled for 6 h with tritiated thymidine in the presence of peptide. For screening purposes, the effect on DNA-synthesis was assayed as incorporation of [3H]-thymidine into acid-insoluble material. For a more exact estimate, parallel cultures were prepared for autoradiography and the fraction of labelled nuclei was determined by counting. Among the peptides we tested (somatostatin, GRF, TRH, SP, mENK, PHI, VIP, hCT) only somatostatin had any discernible effect on DNA synthesis, with an apparently optimal effect at 10 fM. This concentration is well within the range found in various tissues in vivo and suggests a physiological role for somatostatin in chondrocyte growth regulation. Further experiments are required, however, to clarify by which mechanism somatostatin influences the cells and whether the peptide interacts with other growth factors such as the IGFs.

Animals↗
PubMed1987

Cell fractions from rat rib growth cartilage. Morphological and X-ray microanalytical investigation.

For in vitro studies of differentiation and proliferation of chondrocytes, a need arose to prepare enriched cell fractions for analysis of the effects of different growth promoting factors. Therefore chondrocytes were isolated from rat rib growth cartilage in young rats by collagenase digestion and subsequently three cell fractions were prepared by centrifugation in a step gradient of Percoll. In a previous paper, matrix molecules synthesized by each fraction were characterized biochemically. In the present study, ultrastructure and elemental content of the fractionated chondrocytes were analyzed by scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray microanalysis. DNA-synthetic activity was measured by means of autoradiography of 3H-thymidine incorporating cells. Both morphology and elemental concentrations differed between fractions and were characteristic for each fraction. The cell fraction with the lowest density consisted of large, polygonal cells that became flattened in culture. The reduced synthetic activity and markedly lowered K content of these cells suggest that they originate from the hypertrophic zone of the growth plate. The cells in the fraction with the highest density were rather homogeneous in size and shape, and had a well developed rough endoplasmic reticulum and Golgi complex, characteristic of proliferating and resting chondrocytes. Concentrations of P and K were also significantly higher in this fraction. The fraction with intermediate density contained an admixture of cells with a predominance of proliferating cells with high DNA-synthetic activity.

Animals↗
PubMed1986

Biomechanical and biochemical studies of tendon healing after conservative and surgical treatment.

Based on clinical studies, it has been proposed that conservative treatment of Achilles tendon ruptures is feasible. However, no biomechanical or biochemical confirmation of this proposal has been presented. In the present investigation the biomechanical and biochemical properties of tendons treated surgically and conservatively after transverse tenotomy were studied. Sixty-eight New Zealand White rabbits were used. A transverse tenotomy of the plantaris longus tendon of the left hind leg was performed. In half of the animals the tenotomy was repaired with a criss-cross silk suture and the limb was immobilized; the other half were treated with immobilization alone. The immobilization was maintained for 4 weeks with a long-leg plastic splint in both groups. After 4, 8, and 16 weeks the tendons were examined regarding biomechanical and biochemical parameters. There were no detectable differences in biomechanical parameters or in tendon elongation between the groups, nor was there any difference in the total hydroxyproline content, the amount of mature and of immature collagen, or the water content. The present findings are compatible with previous favorable reports on conservative treatment of Achilles tendon ruptures and thus suggest interesting clinical possibilities.

Achilles Tendon↗
PubMed1986

Cell fractions from rat rib growth cartilage. Biochemical characterization of matrix molecules.

In an attempt to isolate and characterize the putative target cells for growth hormone, chondrocytes were isolated from rat rib growth cartilage and fractionated by centrifugation in a discontinuous Percoll gradient. This resulted in three cell fractions with differing properties. The fraction with the lowest density consisted mainly of large, lipid-containing cells which became flattened in subsequent culture. The cells in this fraction were fair collagen producers but synthesized only minor amounts of proteoglycans and apparently no proteoglycan aggregates. These cells probably originate in the hypertrophy zone of the growth plate. The fraction with highest density, on the other hand, consisted of small cells which upon cell culture became polygonal and surrounded with refractile matrix. They synthesized less collagen, but more proteoglycans than the low-density fraction. The proportion of proteoglycan aggregates was rather low (10-20%) but otherwise the proteoglycans were similar to those synthesized by other chondrocytes. This cell fraction was tentatively identified as cells from the upper part of the growth plate. Finally, the middle fraction was heterogeneous, consisting of cells of varying shape. This fraction synthesized large amounts of both collagen and proteoglycans. In all three cell fractions, type II collagen predominated. There were also minor amounts of (1a, 2a, 3a) collagen, and, in the two denser fractions, of type I collagen.

Animals↗
PubMed1986

The influence of indomethacin on collagen synthesis during tendon healing in the rabbit.

The influence of indomethacin on collagen synthesis in intact and healing plantaris longus tendons in the rabbit was investigated. Forty-four male New Zealand White rabbits were subjected to a standardized trauma (tenetomy + repair) on the left hindlimb. Half of the animals were subsequently treated with indomethacin, 10 mg/kg per day orally, and the other half with placebo. After 2 and 4 weeks the rabbits were injected intravenously with 3H-proline and killed 18 h later. Indomethacin affected the collagen metabolism differently depending on whether the tendons were involved in wound healing or not. In intact tendons the drug caused a small general inhibition of collagen synthesis. In the healing tendon there was a shift towards the synthesis of more insoluble collagen with little effect on the total synthesis. After 4 weeks there was also a slight but significant decrease in the amount of hydroxyproline in the most soluble collagen fraction from the tenotomized, indomethacin treated tendons.

Animals↗
PubMed1986

Phenotype modulation in primary cultures of smooth-muscle cells from rat aorta. Synthesis of collagen and elastin.

Early in primary culture, arterial smooth-muscle cells undergo a transition from a contractile to a synthetic phenotype. This process includes the loss of myofilaments and of contractility. At the same time, an extensive rough endoplasmic reticulum and a large Golgi complex are formed, and active synthesis of DNA, RNA and proteins commences. In the present study, chemical and immunocytochemical methods were used to investigate the production of extracellular-matrix proteins in relation to this change in phenotypic properties. The results showed that the phase of rapid cellular proliferation that follows the structural modulation of smooth-muscle cells is associated with high rates of collagen and elastin synthesis, as measured by the incorporation of 3H-proline into 3H-hydroxyproline and 3H-valylproline, respectively. SDS-polyacrylamide gel electrophoresis and fluorography indicated that type-I collagen is the main collagen species synthesized by these cells. Smaller amounts of type-V collagen and (although not definitively identified) type-III collagen were also detected. Indirect immunofluorescence and immunoelectron microscopy demonstrated that smooth-muscle cells surround themselves with an incomplete basement membrane, containing laminin and type-IV collagen, and thin fibrils of type-I collagen. Adjacent to these fibrils, aggregates of amorphous, elastin-like material were also found. Our observations confirm and extend earlier notions of a close similarity between the behaviour of arterial smooth-muscle cells during in vitro cultivation and during the early stages of the formation of atherosclerotic lesions.

Animals↗
PubMed1986

Anthralin stick (Anthraderm) in the treatment of mosaic warts.

Thirty patients having mosaic warts of the soles for 2 years (range 3 months-6 years) were treated daily with a wax-based anthralin stick supplemented by weekly paring. Six patients dropped out, because they failed to appear for follow-up. Of the remaining patients 17/24 cleared, whereas the warts persisted in 7/24. Although the trial was an open study, this result can hardly be explained by placebo effect since mosaic warts are notoriously resistant to treatment.

Anthracenes↗
PubMed1985

Effect of human growth hormone on proteoglycan synthesis in cultured rat chondrocytes.

We have previously demonstrated that hGH stimulates DNA synthesis in cultured chondrocytes in the absence of serum. The present study is concerned with the effects of hGH on proteoglycan synthesis by cultured chondrocytes. Chondrocytes were isolated from rat rib growth cartilage by collagenase digestion, plated in plastic dishes, transferred to serum-free MCDB 104 medium, and incubated for 24 h to establish growth arrest. The cultures were then preincubated for 0-24 h with various concentrations of hGH and ovine prolactin (oPrl) and finally pulse-labelled for 30 min with radioactive sulphate in the presence of hormone. hGH, but not oPrl, stimulated sulphate incorporation with an apparent maximum at 50 ng/ml (approximately 170%). The stimulatory effect was apparent after 2 h and maximal after 3h preincubation. After 12 h the stimulatory effect had decreased to insignificant levels. Qualitative analysis of isolated proteoglycans indicated that the stimulation of sulphate incorporation by hGH is exerted at the level of protein synthesis with little effect on glycosylation and sulphation. Further experiments are required to demonstrate whether the stimulatory effect on proteoglycan synthesis is a specific phenomenon or represents one aspect of a general stimulation on cell metabolism in preparation for DNA synthesis.

Animals↗
PubMed1984

Analysis of collagen types synthesized by rabbit ear cartilage chondrocytes in vivo and in vitro.

This study compares the collagen types present in rabbit ear cartilage with those synthesized by dissociated chondrocytes in cell culture. The cartilage was first extracted with 4M-guanidinium chloride to remove proteoglycans. This step also extracted type I collagen. After pepsin solubilization of the residue, three additional, genetically distinct collagen types could be separated by fractional salt precipitation. On SDS (sodium dodecyl sulphate)/polyacrylamide-gel electrophoresis they were identified as type II collagen, (1 alpha, 2 alpha, 3 alpha) collagen and M-collagen fragments, a collagen pattern identical with that found in hyaline cartilage. Types I, II, (1 alpha, 2 alpha, 3 alpha) and M-collagen fragments represent 20, 75, 3.5, and 1% respectively of the total collagen. In frozen sections of ear cartilage, type II collagen was located by immunofluorescence staining in the extracellular matrix, whereas type I collagen was closely associated with the chondrocytes. Within 24h after release from elastic cartilage by enzymic digestion, auricular chondrocytes began to synthesize type III collagen, in addition to the above-mentioned collagens. This was shown after labelling of freshly dissociated chondrocytes with [3H]proline 1 day after plating, fractionation of the pepsin-treated collagens from medium and cell layer by NaCl precipitation, and analysis of the fractions by CM(carboxymethyl)-cellulose chromatography and SDS/polyacrylamide-gel electrophoresis. The 0.8 M-NaCl precipitate of cell-layer extracts consisted predominantly of type II collagen. The 0.8 M-NaCl precipitate obtained from the medium contained type I, II, and III collagen. In the supernatant of the 0.8 M-NaCl precipitation remained, both in the cell extract and medium, predominantly 1 alpha-, 2 alpha-, and 3 alpha-chains and M-collagen fragments. These results indicate that auricular chondrocytes are similar to chondrocytes from hyaline cartilage in that they produce, with the exception of type I collagen, the same collagen types in vivo, but change their cellular phenotype more rapidly after transfer to monolayer culture, as indicated by the prompt onset of type III collagen synthesis.

Animals↗
PubMed1984

Normal thoracic aortic diameters by computed tomography.

Although computed tomography (CT) has played an important role in evaluation of the thoracic aorta, no standards for aortic dimensions exist. To establish the range of normal variation of aortic diameters, a retrospective study of 102 chest CT studies in adults without clinical evidence of hypertension, diabetes, cardiovascular disease, or renal disease was performed. The coronal aortic diameter was measured at three levels: just beneath the aortic arch, just above the aortic valve, and at the level of the diaphragm. These measurements showed substantial variation according to age, sex, and thoracic vertebral body width. The ratio between the ascending and descending limbs of the aorta varied markedly with age; younger individuals had significantly higher ratios than older age groups. Knowledge of these values allows more precise CT evaluation in suspected aortic disease, specifically reducing the potential for "overinterpretation" of the normal, but prominent, ascending aortic root.

Adult↗
PubMed1983

Synthesis and secretion of proteoglycans by cultured chondrocytes. Effects of monensin, colchicine and beta-D-xyloside.

Chondrocytes, isolated from elastic ear cartilage of young rabbits, were grown in monolayer cultures in Ham's F-12 medium. Synthesis and secretion of macromolecules were monitored by labelling with radioactive precursors and the effect of monensin and other experimental agents was investigated. Monensin caused an inhibition of the incorporation of precursors into macromolecular material and a moderate intracellular accumulation when used in higher concentrations. The effect was more pronounced for 35SO4 than for 3H-labelled glucose or proline. p-Nitrophenyl-beta-D-xyloside alleviated this inhibition to some extent, but there was a concomitant increase in the amount of intracellular labelled material. Colchicine and monensin together caused a severe inhibition of the incorporation of 35SO4 and a marked shift of the label to the intracellular compartment. Colchicine also increased the sensitivity of the cells to monensin, lowering the minimal effective concentration about one order of magnitude. The latter results are consistent with the idea that cytoplasmic microtubules have a stabilizing function on the secretory pathways and, that their removal by colchicine, causing a 'randomizing' of the Golgi complex, makes these pathways more vulnerable to monensin.

Animals↗
PubMed1983

Synthesis of proteoglycans, collagen, and elastin by cultures of rabbit auricular chondrocytes--relation to age of the donor.

Chondrocytes were isolated from the auricular cartilage of rabbits, aged 1 week to 30 months, and grown in short-term cell culture. The cells from the 1-week animals were small, polygonal, and mononucleated, while the chondrocytes from the older animals were larger, rounded, and frequently binucleated. The synthesis of proteoglycans, collagen, and elastin was determined by isotope incubation. Chemical characterization of the proteoglycans was also performed. The production of the matrix macromolecules showed a clear age dependence with peak synthesis occurring at different ages. Proteoglycans were actively synthesized by chondrocytes from all age groups with a broad maximum between 2 weeks and 5 months followed by a sharp decline to about 50% of the 1-week level at 12-30 months. Collagen synthesis peaked at 2 weeks, declining progressively thereafter to about 60% of the 1-week level at 30 months. Elastin synthesis was highest in the 1-week cultures and thereafter fell quickly to very low levels. In all age groups the chondrocytes synthesized predominantly cartilage-typic proteoglycans, i.e., large aggregate forming molecules containing chondroitin sulfate. Monomers and aggregates showed a size maximum at 2-8 weeks. The degree of sulfation of the chondroitin sulfate and the proportion of 6-sulfate increased with age. These findings support the concept of "age programs" for the biosynthesis and turnover of different matrix macromolecules.

Aging↗