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Biomedical subjects

M de Jong

Publications and source records attributed to M de Jong.

At least 109 records · Page 6Linked to original sources
PubMed1987

Increased bone formation and decreased bone resorption in fetal mouse calvaria as a result of intermittent compressive force in vitro.

We have shown earlier that hypertrophic chondrocytes of growth plate cartilage in vitro react to an intermittent compressive force (ICF) of physiological magnitude by an increased calcification of the matrix. In this communication, we report the influence of ICF on bone metabolism, i.e., osteoblastic and osteoclastic activity, using fetal mouse calvaria in vitro. Seventeen-day-old calvaria were cultured for 5 days under control conditions (atmospheric pressure), or under the influence of ICF. ICF was generated by intermittently compressing the gas phase above the culture medium (130 mbar, 0.3 Hz). Osteoblastic activity was monitored by measuring alkaline phosphatase (AP) activity and 45Ca incorporation into the bone mineral. Osteoclastic resorption of the mineral phase was monitored by measuring the release of 45Ca from prelabeled bone rudiments. In addition, the total mineral content (Ca and Pi) of the calvaria was determined. Exposure to ICF resulted in a significant increase in bone formation, indicated by an enhanced alkaline phosphatase activity and increased incorporation of 45Ca, as well as a decreased bone resorption. The combined effects led to a net increase in mineral content per calvarium of some 16%. We conclude that both osteoblasts and osteoclasts are affected by intermittent compressive force. Osteoblasts are stimulated, and osteoclasts are inhibited in their activity and/or growth. The effect of ICF on osteoblasts is comparable with the effect on fetal growth plate chondrocytes; both cell types respond to ICF by an increase in calcium-phosphate mineral deposition in the matrix. The lower bone resorption may be a direct effect of ICF on osteoclasts, but it is also possible that osteoblasts play an intermediate role.

Alkaline Phosphatase↗
PubMed1986

Periplasmic accumulation of truncated forms of outer-membrane PhoE protein of Escherichia coli K-12.

In order to localize the information within PhoE protein of Escherichia coli K-12 required for export of the protein to the outer membrane, we have generated deletions throughout the phoE gene. Immunocytochemical labelling on ultrathin cryosections revealed that the polypeptides encoded by the mutant alleles are transported to, and accumulate in, the periplasm. These results show that, except for the signal sequence, there is no specific sequence within the PhoE protein that is essential for transport through the cytoplasmic membrane. The overall structure of the protein, rather than a particular sequence of amino acids, seems to be important for assembly into the outer membrane.

Autoradiography↗
PubMed1986

Ultrastructural study of fluoride-induced in-vitro hypermineralization of enamel in hamster tooth germs explanted during the secretory phase of amelogenesis.

The effects of fluoride (5, 10 and 20 parts/10(6) F-) were studied in vitro with light and electron microscopy in 5-day-old hamster maxillary second molar tooth germs explanted when most of the ameloblasts are in the secretory phase, and cultured for 24 h in the presence of F-. F- at all doses investigated induced hypermineralization of that enamel which had been secreted in vivo just prior to exposure to F-. The most intense hypermineralization was in the aprismatic enamel near the cervical loop region, where the in-vivo enamel layer was thinnest and gradually decreased (but was not abolished) with the increasing thickness of in-vivo formed enamel in the more mature parts of the enamel organ. The fluoride-induced hypermineralization in the aprismatic enamel layer did not stain at all with dilute toluidine blue solution and was therefore indistinguishable from the underlying dentine in light micrographs. The hypermineralization was due to growth in thickness of the enamel crystals, which in the aprismatic enamel layer resulted in a lateral fusion of all the enamel crystals. Thus fluoride administered during the secretory phase of enamel formation decontrols or even abolishes enamel crystal growth in length and promotes crystal growth in thickness so producing the hypermineralization of the pre-fluoride enamel. Enamel matrix secreted in the presence of fluoride did not mineralize.

Amelogenesis↗
PubMed1986

Biochemical and immunological characterization of cell surface proteins of Pasteurella multocida strains causing atrophic rhinitis in swine.

In a previous paper (B. Lugtenberg, R. van Boxtel, and M. de Jong, Infect. Immun., 46:48-54, 1984) we showed that among 34 isolates from swine the membrane protein and lipopolysaccharide (LPS) patterns, as analyzed by sodium dodecyl sulfate-gel electrophoresis, could be classified into three and six patterns, respectively. In all cases a certain LPS pattern was correlated with a certain protein pattern. Certain combinations of types of cell surface proteins and LPSs were correlated with pathogenicity, the latter property being judged by the guinea pig skin test. In the present paper the immunological and biochemical properties of cell surface constituents were analyzed. The reaction between electrophoretically separated cell surface constituents with guinea pig and sow antisera showed that LPS as well as several proteins were immunogenic. Among these is protein H, whose electrophoretic mobility is the main criterium for typing of cell envelope protein patterns. Protein H was the most heavily labeled component when whole cells were iodinated by the Iodo-Gen procedure showing its accessibility at the cell surface. These properties of protein H make it an attractive vaccine candidate. Further biochemical analyses revealed that protein H shares many properties with pore proteins of members of the family Enterobacteriaceae. One of these properties, association between pore proteins and peptidoglycan, was used as the basis for a simple procedure developed to partially purify protein H.

Animals↗
PubMed1985

Site-directed mutagenesis of the Escherichia coli chromosome near oriC: identification and characterization of asnC, a regulatory element in E. coli asparagine metabolism.

We developed a new method for the specific mutagenization of the E. coli chromosome. This method takes advantage of the fact that a pBR322 plasmid containing chromosomal sequences is mobilizable during an Hfr-mediated conjugational transfer, due to an homologous recombination between the E. coli Hfr chromosome and the pBR322 derivative. Transconjugants are screened with a simple selection procedure for integration of mutant sequences in the chromosome and loss of pBR322 sequences. Using this method we specifically inactivated several genes near the E. coli replication origin oriC. We found that a gene coding for asparagine synthetase A. This regulatory mechanism was investigated in detail by determining in vivo regulation of asnA promoter activity by the 17kD protein under different growth conditions. Results obtained also suggest a general regulatory role of the 17kD protein in E. coli asparagine metabolism. Therefore the 17kD gene is proposed to be renamed asnC.

Asparaginase↗
PubMed1984

Specific localization of In-111-labeled monoclonal antibody versus 67-Ga-labeled immunoglobulin in mice bearing human breast carcinoma xenografts.

A murine monoclonal antibody reacting with more than 95% of all breast cancers was radiolabeled with In-111 and injected IP into nude mice bearing human breast carcinoma xenografts, together with Ga-67-labeled normal mouse immunoglobulin. Images were produced with a gamma camera in dual isotope mode. Tumors could be localized clearly with In-111-labeled specific monoclonal antibody, but improved visualization was obtained after computer-assisted subtraction of the image with Ga-67-labeled nonspecific immunoglobulin. The tumor-to-tissue contrast was improved from 2.3 to 5.9 after subtraction. Imaging with In-111-radiolabeled monoclonal antibody was superior to imaging with iodinated antibody. For the first time it was shown that images of two chemically related isotopes, Ga-67 and In-111, coupled to nonspecific and specific antibody, respectively, and simultaneously injected, can be subtracted to show the preferential uptake of the specific antibody in the tumor. As these isotopes are routinely used in clinical practice this technique may prove to be more practical for immunodetection of tumors in patients than existing imaging techniques.

Animals↗
PubMed1984

Biochemical and immunological analyses of the cell surface of Bordetella bronchiseptica isolates with special reference to atrophic rhinitis in swine.

The guinea-pig skintest was used to test the pathogenic character of nine Bordetella bronchiseptica isolates derived from a number of different animals. One isolate was non-pathogenic, one showed a doubtful reaction whereas the others were pathogenic. Analysis of the cell envelope protein patterns by sodium dodecyl sulphate polyacrylamide gel electrophoresis revealed only minor differences. Two major protein bands and at least thirty five minor bands were observed. The major protein with an apparent molecular weight of 37000 has properties similar to those of pore proteins of Enterobacteriaceae. Lipopolysaccharides (LPS), analysed by the same technique, could be separated into two fractions, LPS-I and LPS-II. The electrophoretic mobilities of the LPS of the strains were indistinguishable from each other with the exception of that of the non-pathogenic strain, which also differed serologically from that of the other strains. All sera of animals which had been successfully vaccinated with whole B. bronchiseptica cells showed a positive reaction with LPS-I whereas antibodies against the 37000 dalton protein, LPS-II as well as against several other proteins, were also detected in several sera. These results strongly suggest that LPS-I is a protective antigen. LPS-I and the 37000 dalton protein are accessible to antibodies in whole cells. This protein as well as a 28000 dalton protein were found to be located at the cell surface using iodination of whole cells with Iodo-Gen.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Atrophic rhinitis in swine: correlation of Pasteurella multocida pathogenicity with membrane protein and lipopolysaccharide patterns.

Cell envelope proteins and lipopolysaccharides (LPS) of Pasteurella multocida strains associated with atrophic rhinitis in swine were compared by using sodium dodecyl sulfate gel electrophoresis. Among 34 strains, three different types of cell envelope protein patterns, named I (16 strains), II (3 strains), and III (15 strains), could be distinguished. These differences were based on the electrophoretic mobility of the major protein, designated as protein H. Comparison of cell envelope protein type and pathogenicity of the strain, the latter property predicted by the guinea pig skin test, revealed that all type I strains, 6 of 15 type III strains, and none of the type II strains were pathogenic. Although pathogenicity has been correlated with extracellular toxin activity, no protein could be detected in either the cell envelopes or in the extracellular fluid that absolutely correlated with pathogenic strains. Electrophoretic analysis of the LPS revealed that all strains possessed low-molecular-weight LPS, which is inconsistent with the presence of a classical O antigen. The method allowed the detection of at least six types of LPS, which often coincided with a certain cell envelope protein type and with the presence or absence of the pathogenic character of the strain. These results strongly suggest that the sampled swine carry a limited number of P. multocida clones, in each of which the patterns of cell envelope proteins and LPS, as well as the presence or absence of the ability to produce extracellular toxin, are well conserved. Therefore, the possibility is discussed that sodium dodecyl sulfate gel electrophoresis of cell envelope proteins and LPS may be used for the prediction of the pathogenic character of part of the strains. Finally, the typing of strains based on cell envelope protein patterns might contribute to the development of vaccines containing outer membrane proteins as protective antigens.

Animals↗