Search PubMed⌕ Search

Biomedical subjects

J van der Zwan

Publications and source records attributed to J van der Zwan.

9 recordsLinked to original sources
PubMed2001

Dinuclear alkyldiamine platinum antitumor compounds: a structure-activity relationship study.

Six related dinuclear trans-platinum complexes, with the formula [[trans-PtCl(2)(NH(3))(L)](2)(mu-H(2)N(CH(2))(n)NH(2))](2+) (L = pyridine, 2-picoline, 4-picoline; n = 4, 6) and chloride or nitrate anions, are compared with known cytotoxic dinuclear compounds (L = NH(3); n = 4, 6) that overcome cisplatin resistance. The cytotoxicity of the compounds was determined in L1210 murine leukemia and L1210/2, a cisplatin-resistant derivative. Unlike the L = NH(3) compounds, the substituted n = 4 compounds are more susceptible toward the resistance mechanisms in L1201/2. The n = 6 compounds, however, have comparable IC(50) values in both cell lines. In general, the substituted compounds are less cytotoxic than their NH(3) counterparts. After incubation with equimolar concentrations, the amount of platinum bound to cellular DNA was determined. The compounds show comparable binding, except for the sterically hindered 2-picoline compounds that bind significantly less. The amounts of platinum bound to DNA do not correlate with the cytotoxicity data. As DNA is considered to be the cellular target of platinum antitumor drugs, structural details of the DNA adducts probably account for the differences in cytotoxic activity.

Animals↗
PubMed1998

[Condylar hyperplasia. Early detection is desired].

When single-sided excessive condylar growth is detected in time, removal of the affected condyle is sufficient. In cases of late detection, extensive surgery of upper and lower jaw and the chin may be necessary.

Adult↗
PubMed1997

The solution structure of serine protease PB92 from Bacillus alcalophilus presents a rigid fold with a flexible substrate-binding site.

BACKGROUND: Research on high-alkaline proteases, such as serine protease PB92, has been largely inspired by their industrial application as protein-degrading components of washing powders. Serine protease PB92 is a member of the subtilase family of enzymes, which has been extensively studied. These studies have included exhaustive protein engineering investigations and X-ray crystallography, in order to provide insight into the mechanism and specificity of enzyme catalysis. Distortions have been observed in the substrate-binding region of subtilisin crystal structures, due to crystal contacts. In addition, the structural variability in the substrate-binding region of subtilisins is often attributed to flexibility. It was hoped that the solution structure of this enzyme would provide further details about the conformation of this key region and give new insights into the functional properties of these enzymes. RESULTS: The three-dimensional solution structure of the 269-residue (27 kDa) serine protease PB92 has been determined using distance and dihedral angle constraints derived from triple-resonance NMR data. The solution structure is represented by a family of 18 conformers which overlay onto the average structure with backbone and all-heavy-atom root mean square deviations (for the main body of the molecule) of 0.88 and 1.21 A, respectively. The family of structures contains a number of regions of relatively high conformational heterogeneity, including various segments that are involved in the formation of the substrate-binding site. The presence of flexibility within these segments has been established from NMR relaxation parameters and measurements of amide proton exchange rates. CONCLUSIONS: The solution structure of the serine protease PB92 presents a well defined global fold which is rigid with the exception of a restricted number of sites. Among the limited number of residues involved in significant internal mobility are those of two pockets, termed S1 and S4, within the substrate-binding site. The presence of flexibility within the binding site supports the proposed induced fit mechanism of substrate binding.

Amino Acid Sequence↗
PubMed1991

[The impacted upper cuspid].

Impacted upper cuspids may give rise to problems, such as the formation of cysts and the resorption of adjacent teeth. Early diagnosis (before the age of 12) is important. Proper timing of extraction of the deciduous cuspid may lead to spontaneous correction. When the position of the cuspid is unclear, orthopantomography and a lateral skull film may be helpful. Palatally impacted cuspids should be exposed surgically and moved into position by orthodontic treatment. Labially impacted cuspids are exposed by relocation of an attached gingival flap. The experience of the authors with the treatment of 81 patients are reported.

Adolescent↗
PubMed1981

Sagittal chin rotation of the prognathic edentulous mandible.

In edentulous patients with a prognathic mandible, a pronounced chin and extensive resorption of the lower alveolar ridge, the commonly used techniques of ramus osteotomy and chin reduction will not give optimal results in the majority of cases. The solution of this problem can be obtained by mandibular body ostectomy and a sagittal rotation of the frontal part of the lower jaw. By this operation the originally horizontally orientated upper plane of the chin area is placed in a more vertical position. This operative technique gives a better predictable facial contour than the conventional methods. It causes no unfavorable displacement of the lower lip and, which is very important, it gives an absolute increase of height of the lower alveolar ridge and a more favorable inclination of the frontal part of the alveolar process from a prosthetic point of view. The problems encountered and the results obtained by this technique will be demonstrated by a short case presentation.

Adult↗
PubMed1980

The vertical avulsion flap.

Unilateral vertical tangential maxillofacial trauma may result in a combination of a certain number of charcteristic lesions. Although composed of wounds and fractures in the upper, middle and lower third of the face, this form of injury can be considered to be a separate distinct entity. Two patients are described, illustrating this type of injury. Both also sustained trauma of the ipsilateral shoulder.

Accidents, Traffic↗