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J Bergsma

Publications and source records attributed to J Bergsma.

At least 19 recordsLinked to original sources
PubMed1995

Site-directed mutations in tyrosine 195 of cyclodextrin glycosyltransferase from Bacillus circulans strain 251 affect activity and product specificity.

Tyrosine 195 is located in the center of the active site cleft of cyclodextrin glycosyltransferase (EC 2.4.1.19) from Bacillus circulans strain 251. Alignment of amino acid sequences of CGTases and alpha-amylases, and the analysis of the binding mode of the substrate analogue acarbose in the active site cleft [Strokopytov, B., et al. (1995) Biochemistry 34, (in press)], suggested that Tyr195 plays an important role in cyclization of oligosaccharides. Tyr195 therefore was replaced with Phe (Y195F), Trp (Y195W), Leu (Y195L), and Gly (Y195G). Mutant proteins were purified and crystallized, and their X-ray structures were determined at 2.5-2.6 angstrum resolution, allowing a detailed comparison of their biochemical properties and three-dimensional structures with those of the wild-type CGTase protein. The mutant proteins possessed significantly reduced cyclodextrin forming and coupling activities but were not negatively affected in the disproportionation and saccharifying reactions. Also under production process conditions, after a 45 h incubation with a 10% starch solution, the Y195W, Y195L, and Y195G mutants showed a lower overall conversion of starch into cyclodextrins. These mutants produced a considerable amount of linear maltooligosaccharides. The presence of aromatic amino acids (Tyr or Phe) at the Tyr195 position thus appears to be of crucial importance for an efficient cyclization reaction, virtually preventing the formation of linear products. Mass spectrometry of the Y195L reaction mixture, but not that of the other mutants and the wild type, revealed a shift toward the synthesis (in low yields) of larger products, especially of beta- and gamma- (but no alpha-) cyclodextrins and minor amounts of delta-, epsilon-, zeta- and eta-cyclodextrins.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1995

Psychosocial adaptation to stoma surgery: a review.

During the last decade strong improvements have been made in the medical care of patients with a digestive tract stoma, particularly with regard to nursing skills and to the quality of collecting material for faecal products. Scientific investigation into the psychosocial adjustment of patients after stoma surgery has intensified as well, giving us indications for quality of life. These developments induced a review of the actual state of affairs in psychological issues. After evaluating the results of psychosocial stoma research, it can be concluded that the technical improvements in stoma care during the past decade did not result in a decline in psychosocial problems after stoma surgery. However, there are some serious problems when interpreting the results of studies in this field of investigation. Stoma surgery is not per se solely responsible for the reported psychosocial problems, first, because many conclusions are based on research studies with poor design and, second, because these studies lack a theoretical framework within which the process of psychosocial adjustment has been measured and explained. This review assesses the most current developments and controversies in this field.

Adaptation, Psychological↗
PubMed1994

Illness, the mind, and the body: cancer and immunology: an introduction.

From the sixties on it has become clear how the human physical condition could be influenced by human behavior. Although hypothesis were lacking to understand these connections, nursing research especially proved how systematically introduced patient behavior during illness and hospitalization could induce better recovery results and better prognosis for the patient. Information and attitude proved to be crucial elements in these processes of improved patient expectations. It took less than two decades to get to the insights we have in 1994. Recent research shows the interlocking mechanisms of nervous and endocrine systems with the immune system as significantly being influenced by behavior and especially psychic and or psychosocial stress. This special issue of Theoretical Medicine briefly describes the historical development with contributions on the most recent state of the scientific art. These developments are emphasized by discussion on the clinical reality of the (breast) cancer patient and recent findings on the complexity of the prevalence of cancer in epidemiology. An attempt is made to consider practical consequences of the actual knowledge if applied to patient care.

Animals↗
PubMed1994

The trauma triangle.

Recent research supports the hypothesis that more active engagement of the patient in occurring illnesses improves quality of life and probably even life expectancy. In this study experience and theoretical knowledge from psychotherapy is transplanted to clinical practice in order to improve the physician's engagement in the patient-disease relationship. By defining severe and long-term illnesses as a psychotrauma, the transfer of the psychotherapeutical model leads to the creation of a new triangular relationship: patient-illness-doctor. Practical examples are used as illustrations for the conceptual differences between psychotherapy and clinical medicine. Options for dialogue show the difference between adaptation ("learning to live with") and adjustment (active coping strategies and controlling). The hypothesis is that a better dialogue will reduce illness-related stress, giving the patient better and more effective access to personal psychic and physical support systems.

Adaptation, Psychological↗
PubMed1992

[Support following pregnancy termination for genetic indications: experiences of involved women and their partners].

By means of semistructured interviews with 40 women and their partners data were collected concerning on the one hand the care and support and on the other the grieving after termination of pregnancy performed because the child appeared to be genetically affected. Crucial in the grieving process is having to choose personally for or against termination of the pregnancy. This grieving process can be complicated by factors such as uncertainty concerning either the evidence of the disease or its prognosis, high recurrence risk, negative self-esteem, feelings of failure and pre-existent relational or personal problems. Clear and complete counselling, combined with structural support during the hospital stay, proves to be the basis of adequate care. Follow-up interviews after the hospital stay play a supporting part, both for the hospital workers and for the couple involved.

Abortion, Induced↗
PubMed1990

Maltodextrin-dependent crystallization of cyclomaltodextrin glucanotransferase from Bacillus circulans.

Crystals of cyclomaltodextrin glucanotransferase from Bacillus circulans (EC 2.4.1.19) suitable for high-resolution X-ray analysis were obtained by vapor diffusion against 60% (v/v) 2-methyl 2,4-pentanediol buffered with 100 mM-sodium Hepes, pH 7.55. The crystals have P2(1)2(1)2(1) space group symmetry, with a = 120.4 A, b = 110.9 A and c = 66.4 A, and contain one molecule of 68,000 in the asymmetric unit. Growth of single enzyme crystals was found to require the presence of either alpha-cyclodextrin, beta-cyclodextrin, gamma-cyclodextrin, or maltose in high molar excess, a requirement that could not be fulfilled by glucose, the basic building block of these compounds. Although the exact role of cyclic and linear maltodextrins in enzyme crystallization is not yet known, we have preliminary evidence that these compounds are degraded by the enzyme in the crystallization droplet.

Bacillus↗
PubMed1990

Problems and coping behaviour of facial cancer patients.

On the basis of an arrangement scheme by Cohen and Lazarus, an investigation has been made into the literature on problems patients experience after having undergone tumour surgery resulting in facial mutilation. Furthermore, the ways in which these patients cope with their problems have been looked at. The greatest problems arise at the interpersonal level, and in particular with intimate (sexual) relationships and with superficial, anonymous contacts. The face is found to be of essential importance in interpersonal relationships. During the first phase of the disease, when all attention is focused on the fact of having cancer, patients especially react with intrapsychic coping mechanisms. Later, after surgery, the problems are mainly concentrated on the inescapable necessity to live with a clearly visible mutilation. At this stage, in order to be able to talk about his experiences, to find recognition; and to adapt his self-image, the patient particularly turns to other people for support. It turned out that the ordering of Cohen and Lazarus' arrangement scheme gives a good outline of the difficulties patients encounter. In addition to this, several psychological theories and concepts offer good explanations for the facts as found.

Adaptation, Psychological↗
PubMed1986

The alpha-macroglobulins from rat plasma: structure, plasma clearance and endocytosis of complexes with subtilisin.

Rat alpha 2M was isolated from plasma of animals which had been treated with stress hormones. Polyacrylamide-gel electrophoresis of the reduced protein in the presence of sodium dodecyl sulfate showed a band with a Mr of 175,000. In a previous work (Biochem. J. 226, 75-84, 1985) we had found that rat alpha 1M consists of two types of subunits with Mr's of 163,000 and 37,000. Like the large subunit of alpha 1M the chain of alpha 2M contained a peptide bond that was susceptible to autolysis and a site that was split by trypsin. Negatively stained free alpha 2M could be distinguished from free alpha 1M under the electron microscope. Radioactively labelled alpha 2M was slowly cleared from plasma, but complexes of the protein with labelled subtilisin were rapidly cleared with first-order kinetics, showing a half-life of about 6 min. These complexes were mainly taken up by the liver, as had previously been described for alpha 1M-subtilisin complexes. Complexes of both macroglobulins competed with each other for uptake, indicating endocytosis via a common receptor.

Animals↗
PubMed1985

Complexes of rat alpha 1-macroglobulin and subtilisin are endocytosed by parenchymal liver cells.

Rat alpha 1-macroglobulin was isolated from plasma. Gel electrophoresis of the denatured and reduced protein showed two bands, with Mr values of 163 000 and 37 000. The large subunit contained an autolytic site. This subunit was also split after reaction of the macroglobulin with trypsin. Electron microscopy showed that the macroglobulin changed towards a more compact conformation after reaction with this proteinase. Subtilisin, or alpha 1-macroglobulin, was labelled with a sucrose-containing radio-iodinated group that stays in lysosomes after endocytosis and breakdown of the tagged protein. After intravenous injection into rats, alpha 1-macroglobulin was cleared from plasma with first-order kinetics, showing a half-life of about 9 h, whereas complexes of alpha 1-macroglobulin and subtilisin were cleared with half-lives of only 3 min. Liver contained about 60% of the label at 30 min after injection of complexes. About 90% of the liver radioactivity was found in parenchymal cells isolated after perfusion of the liver with a collagenase solution. Subcellular fractionation indicated a lysosomal localization of the complexes. We conclude that endocytosis by parenchymal liver cells is the major cause of the rapid clearance of alpha 1-macroglobulin-proteinase complexes from plasma.

Animals↗
PubMed1983

[Letter to nurses].

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Adaptation, Psychological↗
PubMed1983

The properties of citrate transport in membrane vesicles from Bacillus subtilis.

The uptake system for citrate is induced in Bacillus subtilis W23 by growth in the presence of citrate and only membrane vesicles isolated from these cells show energy-dependent citrate uptake. Citrate transport in membrane vesicles is strictly dependent on the presence of divalent cations such as Mg2+, Mn2+, Zn2+, Ba2+, Be2+, Ca2+, Cu2+, Co2+ or Ni2+. The initial rate of citrate transport increases with the divalent cation concentration up to a maximum. The maximum initial rate of citrate uptake is reached with 2 mM Mg2+. The cations form stable chelates with citrate. The metal citrate complex is the transported solute. This is demonstrated for citrate uptake in the presence of Ca2+. Membrane vesicles from citrate-grown cells accumulate Ca2+ and citrate only if both solutes are present. Citrate and Ca2+ are accumulated in equimolar quantities. The uptake of Ca2+ but not of citrate is inhibited by Mg2+. Uptake of the metal-citrate complex is inhibited by the uncoupler carbonylcyanide p-trifluoromethoxyphenyl-hydrazone and in the presence of K+ ions by valinomycin and nigericin. The inhibitory effects correlate with the effects observed on the components of the proton-motive force, indicating that the proton-motive force is a driving force for metal-citrate transport. The number of protons (n) symported with the metal-citrate complex has been determined under different experimental conditions from the steady state levels of citrate accumulation, the electrical potential and pH gradient. This number varies from 1 at pH 4.7 to 2 at pH 8.0.

Bacillus subtilis↗
PubMed1982

Purification and characterization of NADH dehydrogenase from Bacillus subtilis.

NADH dehydrogenase from Bacillus subtilis W23 has been isolated from membrane vesicles solubilized with 0.1% Triton X-100 by hydrophobic interaction chromatography on an octyl-Sepharose CL-4B column. A 70-fold purification is achieved. No other components could be detected with sodium dodecyl sulphate polyacrylamide gel electrophoresis. Ferguson plots of the purified protein indicated no anomalous binding of sodium dodecyl sulphate and an accurate molecular weight of 63 000 could be determined. From the amino acid composition a polarity of 43.8% was calculated indicating that the protein is not very hydrophobic. Optical absorption spectra and acid extraction of the enzyme chromophore followed by thin-layer chromatography showed that the enzyme contains 1 molecule FAD/molecule. The enzyme was found to be specific for NADH. NADPH is oxidized at a rate which is less than 6% of the rate of NADH oxidation. The activity of the enzyme as determined by NADH:3-(4'-5'-dimethyl-thiazol-2-yl)2,4-diphenyltetrazolium bromide oxidoreduction is optimal at 37 C and pH 7.5-8.0. The purified enzyme has a Kapp for NADH of 60 microM and a V of 23.5 mumol NADH/min X mg protein. These parameters are not influenced by phospholipids. The enzyme activity is hardly or not at all affected by NADH-related compounds such as ATP, ADP, AMP, adenosine, deoxyadenosine, adenine and nicotinic amide indicating the high binding specificity of the enzyme for NADH.

Bacillus subtilis↗