Biomedical subjects

J Dam

Publications and source records attributed to J Dam.

7 recordsLinked to original sources

PubMed2000

Complementation between dimeric mutants as a probe of dimer-dimer interactions in tetrameric dihydrofolate reductase encoded by R67 plasmid of E. coli.

The effect of mutations on the interactions between dimers in R67 dihydrofolate reductase (R67 DHFR), a tetrameric enzyme conferring resistance to trimethoprim, was investigated by site-directed mutagenesis combined with phenotypic, enzymatic, and biochemical analysis. Some 14 mutants at two positions involved in a hydrogen bond between dimers were constructed. All were shown to be dimers. However, complementation between pairs of dimeric mutated proteins resulted in the restoration of the enzymatic activity and heterotetramer formation. A combinatorial approach was set up to create efficiently such heterotetramers and identify the complementing pairs of mutations. A dozen of such pairs were found. An accurate method was set up to measure the association of the complementing dimers in a "quasi-isologous" heterotetramer and used to study the effects of mutations and pH on the association. Thus, the pair of proteins bearing respectively the S59A and H62L mutations was shown to form heterotetramers with catalytic properties close to those of the wild-type protein. Its association was as strong as that of the wild-type protein at cytoplasmic pH (6. 5), and was more stable at lower pH values.A double-mutant protein bearing simultaneously the S59A and H62L mutations was produced and analyzed. Its association was weakened by 1.2 kcal/mol as compared to the wild-type enzyme at pH 6.5 but was insensitive to pH. Comparing the energy of association between dimers in the wild-type protein, the heterotetramer and the double mutant allowed us to dissect the effects of the pH and of the molecular context on a subset of interactions between the R67 DHFR subunits.

Amino Acid Substitution↗

PubMed1998

Morning fluoxetine plus evening mianserin versus morning fluoxetine plus evening placebo in the acute treatment of major depression.

In a randomized clinical study the combination of fluoxetine 20 mg daily and mianserin 30 mg daily was compared to fluoxetine 20 mg daily and a mianserin placebo. In total, 34 patients with major depression were randomized, of whom 16 received fluoxetine plus mianserin; 18 patients received fluoxetine plus placebo. Of these patients, 69% completed the planned trial of six weeks in the fluoxetine plus mianserin group while 61% completed in the fluoxetine plus placebo group. In the efficacy analysis (excluding dropouts from the first two weeks of treatment) the combination of fluoxetine and mianserin was superior to fluoxetine and placebo both in observer ratings of depression and in quality of life ratings. However, in the intention-to-treat analysis this difference was not statistically significant. No major side effects were reported. After four weeks of treatment headache was most often seen in the fluoxetine and mianserin combination, while sweating was most often seen in the fluoxetine plus placebo group. No pharmacokinetic interaction in terms of fluoxetine plasma levels was found in the mianserin-treated patients.

Adult↗

PubMed1994

Primary structure and specificity of the major serine proteinase inhibitor of amaranth (Amaranthus caudatus L.) seeds.

A novel member of the potato inhibitor I family of serine proteinase inactivating proteins has been isolated from seeds of grain amaranth (Amaranthus caudatus L.) and characterized. The mature form of the amaranth trypsin/subtilisin inhibitor (ATSI) with pI approximately 8.3 and molecular mass 7887 Da contains 69 amino acids in a sequence showing 33-51% identity with members of the inhibitor I family from other plant families. A minor form with pI approximately 7.8 and same inhibitory properties lacked the N-terminal dipeptide Ala-Arg. In accordance with the reactive-site bond Lys45-Asp46, which was identified by specific cleavage on a subtilisin column, ATSI is a potent inhibitor of trypsin (Ki approximately 0.34 nM) and more weakly of plasmin (Ki approximately 38 nM) and Factor XIIa (Ki approximately 440 nM). However, ATSI also inactivates chymotrypsin (Ki approximately 0.41 nM), cathepsin G (Ki approximately 122 nM) and several alkaline microbial proteinases, including subtilisin NOVO (Ki approximately 0.37 nM). Interestingly, ATSI contains a Trp residue instead of the highly conserved Arg in position 53 (P8'), which is assumed to play a central role in stabilization of the active-site loop during complex formation. ATSI was immediately inactivated by pepsin and hardly represents an antinutritional component in foods or feeds.

Amino Acid Sequence↗

PubMed1994

Leukocyte adhesion molecules in oral lichen planus: a T cell-mediated immunopathologic process.

Oral lichen planus exhibits features of a mucosal type IV immunopathologic process. Adhesion molecules involved in the trafficking and homing of T lymphocytes to the subepithelial compartment were assessed by immunohistochemical methods. Laminin, type IV collagen and type VII collagen extracellular matrix components at the epithelial-connective tissue junction are significantly increased and serve as ligands for beta 1 integrins on lymphocyte membranes. Endothelial-associated intercellular adhesion molecule 1 and extracellular matrix basement membrane components are also significantly increased in the submucosa. Keratinocyte expression of major histocompatibility complex class II molecules and intercellular adhesion molecule 1 may serve as ligands for lymphocyte T cell receptor complex and beta 2 integrins, respectively. These adhesion molecules are probably involved in the trafficking of lymphocytes to the epithelial connective tissue interface in response to as of yet undefined antigens.

Analysis of Variance↗

PubMed1994

Identification and removal of polymer- and aggregate-forming proteins in human plasma albumin preparations.

The presence of the glycoproteins haptoglobin and hemopexin in human plasma albumin (HPA) solutions were demonstrated to be responsible for the formation of polymers and aggregates during heat treatment for 10 h at 60 degrees C. Apart from haptoglobin and hemopexin three other contaminating proteins were identified as transferrin, Gc-globulin and beta 2-glycoprotein. During heat treatment the antigenicity of haptoglobin and hemopexin changed markedly and more than 90% of the antigens appeared as aggregates in the void volume during the following size chromatography. Without loss of albumin haptoglobin and hemopexin were removed from the HPA preparation by lectin (concanavalin A) affinity chromatography. The haptoglobin- and hemopexin-depleted HPA preparation did not form aggregates or polymers during heat treatment.

Biopolymers↗

PubMed1993

Quality and effectiveness of occupational health service evaluated by the providers.

In a debate on the desired occupational health service in The Netherlands all parties involved seemed to be rather unsatisfied with current practice. Therefore a study was set out on the quality of the service to 51 client organizations as seen by the parties involved. In the first phase the viewpoint of the occupational health teams was studied; the second phase among clients was planned later. As it was not feasible to use proper measures of effectiveness, i.e. of outcome in terms of health, the interview was used as method directed at the evaluations of the teams themselves. It focused on the adequacy of the activities of the teams in view of the health problems and risks in the client organization and on the necessary interaction with the clients in order to reach effective service. Although a self-evaluation-method like this has its limitations, results are relevant for the debate on the quality of OHS in The Netherlands. Many occupational health teams want more capacity for preventive activities and to devote more time to these activities to enhance the quality of their service and be more effective. It is argued that for the same purpose the teams themselves should strive for good relations with their clients.

Evaluation Studies as Topic↗

PubMed1990

The revolving door: substance abuse treatment and criminal sanctions for Native American offenders.

Native Americans paroled or released from prison appear to have high recidivism rates both for alcohol abuse and return to incarceration. Tracking of 45 Native American offenders from a prior study on the contribution of alcohol and drugs to offense commission (Grobsmith, 1989a) using both correctional records and personal interview permitted documentation of the type of release (parole, unconditional discharge, with or without referral to treatment) and the individuals' responses to the effectiveness of treatment. These are presented, along with descriptions of the programs available to both inmates and exoffenders or parolees. Alcohol rehabilitation programs in prison and upon release from prison are described, with emphasis on the difficulties treatment programs face in serving exoffenders. Incorporation of indigenous elements or Indian spirituality into treatment is gaining popularity and is espoused by Native Americans as a critical criterion for selection of a treatment program; however, evidence for the increased effectiveness of dependence on exclusively indigenous approaches to alcohol rehabilitation is inconclusive. Syncretic approaches incorporating western and indigenous elements represent those preferred by exoffenders, but choice of treatment program is often determined by funding.

Alcoholism↗