Biomedical subjects

J Roelofsen

Publications and source records attributed to J Roelofsen.

5 recordsLinked to original sources

PubMed1997

Mechanical stimulation of osteopontin mRNA expression and synthesis in bone cell cultures.

We have shown earlier that mechanical stimulation by intermittent hydrostatic compression (IHC) promotes alkaline phosphatase and procollagen type I gene expression in calvarial bone cells. The bone matrix glycoprotein osteopontin (OPN) is considered to be important in bone matrix metabolism and cell-matrix interactions, but its role is unknown. Here we examined the effects of IHC (13 kPa) on OPN mRNA expression and synthesis in primary calvarial cell cultures and the osteoblast-like cell line MC3T3-E1. OPN mRNA expression declined during control culture of primary calvarial cells, but not MC3T3-E1 cells. IHC upregulated OPN mRNA expression in late released osteoblastic cell cultures, but not in early released osteoprogenitor-like cells. Also, in both proliferating and differentiating MC3T3-E1 cells, OPN mRNA expression and synthesis were enhanced by IHC, differentiating cells being more responsive than proliferating cells. These results suggest a role for OPN in the reaction of bone cells to mechanical stimuli. The severe loss of OPN expression in primary bone cells cultured without mechanical stimulation suggests that disuse conditions down-regulate the differentiated osteoblastic phenotype.

3T3 Cells↗

PubMed1995

Mechanical loading stimulates the release of transforming growth factor-beta activity by cultured mouse calvariae and periosteal cells.

We have shown earlier that mechanical stimulation by intermittent hydrostatic compression (IHC) inhibits bone resorption and stimulates bone formation in cultured fetal mouse calvariae (Klein-Nulend et al., 1986, Arthritis Rheum., 29: 1002-1009). The production of soluble bone factors by such calvariae is also modified (Klein-Nulend et al., 1993, Cell Tissue Res., 271:513-517). Transforming growth factor-beta (TGF-beta) is an important local regulator of bone metabolism and is produced by osteoblasts. In this study, the release of TGF-beta activity as a result of mechanical stress was examined in organ cultures of neonatal mouse calvariae, in primary cultures of calvariae-derived osteoprogenitor (OPR) cells, and in more differentiated osteoblastic (OB) cells. Whole calvariae and calvariae-derived cells were cultured in the presence or absence of IHC for 1-7 days and medium concentrations of active as well as total TGF-beta were measured using a bioassay. IHC (maximum 13 kPa, maximal pressure rate 32.5 kPa/sec) was generated by intermittently (0.3 Hz) compressing the gas phase above the cultures. We found that mechanical loading by IHC stimulated the release of TGF-beta activity from cultured calvariae by twofold after 1 day. IHC also stimulated the release of TGF-beta activity from calvariae-derived cells after 1 and 3 days. The absolute amounts of TGF-beta activity released were lower in OPR cells than in OB cells, but the stimulatory effect of IHC was greater in OPR cells. Total TGF-beta (active and bound) released into the medium was not affected by IHC. IHC did not change the dry weight of the organ cultures, nor the DNA or protein content of the cell cultures. These data show that mechanical perturbation of bone cells, particularly OPR cells, enhances the activation of released TGF-beta. We conclude that modulation of TGF-beta metabolism may be part of the response of bone tissue to mechanical stress.

Animals↗

PubMed1995

Mechanical stimulation by intermittent hydrostatic compression promotes bone-specific gene expression in vitro.

In a previous study of the cellular mechanism underlaying Wolff's law we showed that mechanical stimulation by intermittent hydrostatic compression (IHC) increases bone formation in cultured fetal mouse calvariae compared to non-stimulated cultures. To test whether mechanical stimuli may modulate bone-specific gene expression, we studied the effect of IHC on alkaline phosphatase (AP) expression and enzyme activity as well as collagen and actin mRNA levels in neonatal mouse calvariae and calvarial bone cells. Two cell populations, one resembling osteoprogenitor (OPR) cells and another resembling osteoblasts (OB) were obtained from calvariae by sequential digestion. IHC was applied by intermittently (0.3 Hz) compressing the gas- phase of a closed culture chamber (peak stress 13kPa, peak stress rate 32.5 kPas-1). In control cultures of calvariae as well as OB and OPR cells, AP activity and AP-, collagen-, and actin-mRNA levels all decreased after one or more days, with the exception of OPR cell collagen expression which increased during culture. IHC treatment upregulated AP, collagen and actin expression and AP activity in calvariae and OB cells, but decreased collagen expression in OPR cells. These results suggest that treatment with IHC promotes the osteoblastic phenotype in bone organ cultures and in osteoblasts. Osteoprogenitor cells seem to react somewhat differently to mechanical stress than osteoblasts. The loss of bone-specific gene expression under control culture conditions, in the absence of mechanical stimuli, suggests that the mechanical environment is important in maintaining the differentiated phenotype of bone cells, and that IHC treatment partially restores this environment in bone cell- and organ cultures.

Actins↗

PubMed1994

Prenatal diagnosis and fetal outcome of cystic adenomatoid malformation of the lung: case report and historical survey.

Diagnostic ultrasound allows prenatal diagnosis of cystic adenomatoid malformation of the lung from the second trimester onwards throughout pregnancy. If the diagnosis is made before the 24th week of pregnancy, counselling often results in termination of pregnancy. Whether or not this attitude is in agreement with good medical practice is discussed on the basis of our own experience and a review of the literature.

Journal Article↗

PubMed1989

Effect of two monophasic oral contraceptives containing gestodene or desogestrel on serum lipoprotein lipid levels.

Forty-nine healthy women aged 20-35 years who had not been pregnant or using an oral contraceptive (OC) for the previous 3 months were randomized into two groups, one group taking an OC containing 75 micrograms gestodene (GTD) and 30 micrograms ethinyl estradiol (EE), and the other group using an OC with 150 micrograms desogestrel (DSG) and 30 micrograms EE. Fasting blood samples were taken before treatment, and after cycles 3 and 6, between the 18th and the 22nd day of the cycle. Blood lipoprotein lipid levels were measured. Serum total cholesterol did not change significantly in both groups. However, in the first three cycles, serum triglyceride increased by 46% and 40% and HDL-cholesterol by 14% and 8% in the GTD and DSG groups, respectively. The serum LDL level decreased by 6.2% and 11.8%, respectively. Between the third and sixth cycle, no further significant changes were observed, nor did these changes differ significantly between the two groups. In conclusion, both OC preparations exerted small and probably favorable effects on serum lipoprotein lipid levels.

Adult↗