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1.
Ned Tijdschr Geneeskd ; 161: D845, 2017.
Article in Dutch | MEDLINE | ID: mdl-28325158

ABSTRACT

AIM: The use of 'routine outcome monitoring' (ROM) in mental health care has increased widely during the past decade. However, little is known about the use of ROM outcome in daily clinical practice. We investigated to what extent ROM results were reflected in psychotic patients' treatment plans. DESIGN: Cross-sectional study. METHOD: The ROM-Phamous, a ROM-protocol for patients with psychotic disorders in which data is collected on the basis of interviews, questionnaires and physical examination was implemented in the northern Netherlands. A random sample of 100 patients was extracted from the 2010 ROM database (n = 1040), from which we determined the prevalence of a number of problem areas. We then investigated whether these problems were reflected in patients' treatment plans. RESULTS: The sample consisted of 63 men and 37 women, with a mean age of 44 years and a mean duration of illness of 18 years. The prevalence of symptoms and psychosocial problems was 13-37%; the prevalence of cardiovascular risk factors was 11-86%. The majority of problems identified with ROM were not reflected in patients' treatment plans; the opposite also occurred: psychosocial problems, in particular, mentioned in the treatment plans were not always identified with ROM. CONCLUSION: ROM and treatment should ideally be integrated in mental-health services, but currently appear to be separate processes. If improvement of integration of ROM and clinical practice succeeds it could lead to improvement of care for psychiatric patients. Further investigation is warranted. Conflict of interest and financial support: ICMJE forms provided by the authors are available online along with the full text of this article.

2.
J Bacteriol ; 189(14): 5203-9, 2007 Jul.
Article in English | MEDLINE | ID: mdl-17496098

ABSTRACT

Lactococcus lactis, a facultative anaerobic lactic acid bacterium, is known to have an increased growth yield when grown aerobically in the presence of heme. We have now established the presence of a functional, proton motive force-generating electron transfer chain (ETC) in L. lactis under these conditions. Proton motive force generation in whole cells was measured using a fluorescent probe (3',3'-dipropylthiadicarbocyanine), which is sensitive to changes in membrane potential (Delta psi). Wild-type cells, grown aerobically in the presence of heme, generated a Delta psi even in the presence of the F(1)-F(o) ATPase inhibitor N,N'-dicyclohexylcarbodiimide, while a cytochrome bd-negative mutant strain (CydA Delta) did not. We also observed high oxygen consumption rates by membrane vesicles prepared from heme-grown cells, compared to CydA Delta cells, upon the addition of NADH. This demonstrates that NADH is an electron donor for the L. lactis ETC and demonstrates the presence of a membrane-bound NADH-dehydrogenase. Furthermore, we show that the functional respiratory chain is present throughout the exponential and late phases of growth.


Subject(s)
Lactococcus lactis/metabolism , Oxygen/metabolism , Aerobiosis , Cell Membrane/drug effects , Cell Membrane/metabolism , Cell Membrane/physiology , Electron Transport/genetics , Electron Transport/physiology , Fluorescence , Heme/metabolism , Heme/pharmacology , Lactococcus lactis/genetics , Lactococcus lactis/physiology , Membrane Potentials/drug effects , Membrane Potentials/physiology , Models, Biological , Mutation , NAD/metabolism , NADH Dehydrogenase/genetics , NADH Dehydrogenase/metabolism , Oxygen Consumption , Temperature
3.
Behav Res Ther ; 44(5): 715-36, 2006 May.
Article in English | MEDLINE | ID: mdl-16039602

ABSTRACT

This study investigated whether relatively automatic evaluations of food differ between situations and between obese people and lean controls. These evaluations were assessed in the affective priming paradigm (APP) -- a response latency based measure for associations. In Experiment 1, we either focused participants (33 obese and 26 lean controls) on the palatability (restaurant condition) or on the healthiness (health condition) of food, prior to the APP. Independent of weight-status, relatively automatic evaluations of food were based on palatability in the restaurant condition, and on health in the health condition. So, the current focus of attention can shape the way foods are evaluated relatively automatically. In Experiment 2, craving was induced in participants (27 obese and 29 lean controls). Unexpectedly, the craving induction did not achieve its goal of focusing on the palatability of food in general, but just for low-fat foods, possibly because of the health-emphasizing environment -- a hospital. Interestingly, obese people showed a stronger palatability priming effect with increasing levels of initial craving. For normal weight controls the effect was in the same direction, but missed significance. In our environment, palatability of food may be too salient, and health may not be salient enough, influencing automatic food-evaluations.


Subject(s)
Attitude to Health , Dietary Fats/administration & dosage , Food Preferences/psychology , Obesity/psychology , Taste , Adult , Environment , Female , Health Behavior , Humans , Middle Aged , Pilot Projects , Restaurants
4.
Eat Behav ; 6(2): 151-63, 2005 Feb.
Article in English | MEDLINE | ID: mdl-15598602

ABSTRACT

Two experiments are reported that used the affective priming paradigm (Fazio, R. H., Sanbonmatsu, D. M., Powell, M. C., & Kardess, F. R. (1986). On the automatic activation of attitudes. Journal of Personality and Social Psychology, 50, 229-238) to uncover associations with food at a relatively automatic level. Experiment 1 tested the hypothesis that anorexia nervosa (AN; n=22) patients would show less sensitivity to the palatability of foods than unrestrained lean controls (n=27). Results indeed suggested that AN patients did not display a liking of palatable foods over unpalatable foods, whereas unrestrained controls did. Experiment 2 tested the hypothesis that obese people (n=27) would show more sensitivity to the palatability of (high-fat) palatable foods than unrestrained lean controls (n=27) would. However, results suggested that the priming effect was based on health concerns, in that participants showed a preference for low-fat palatable foods over high-fat palatable foods. Average speed of responding and context are discussed as variables influencing the affective priming effect. Taken together, results suggest that food evaluations at a relatively automatic level are controlled by an interaction between participant characteristics, stimuli characteristics, and the specific context.


Subject(s)
Affect , Anorexia Nervosa/psychology , Association , Food Preferences , Obesity/diagnosis , Obesity/psychology , Attitude , Body Mass Index , Dietary Fats , Female , Humans , Psychological Tests
5.
J Cogn Neurosci ; 13(6): 766-85, 2001 Aug 15.
Article in English | MEDLINE | ID: mdl-11564321

ABSTRACT

Luck and Vogel (1997) showed that the storage capacity of visual working memory is about four objects and that this capacity does not depend on the number of features making up the objects. Thus, visual working memory seems to process integrated objects rather than individual features, just as verbal working memory handles higher-order "chunks" instead of individual features or letters. In this article, we present a model based on synchronization and desynchronization of reverberatory neural assemblies, which can parsimoniously account for both the limited capacity of visual working memory, and for the temporary binding of multiple assemblies into a single pattern. A critical capacity of about three to four independent patterns showed up in our simulations, consistent with the results of Luck and Vogel. The same desynchronizing mechanism optimizing phase segregation between assemblies coding for separate features or multifeature objects poses a limit to the number of oscillatory reverberations. We show how retention of multiple features as visual chunks (feature conjunctions or objects) in terms of synchronized reverberatory assemblies may be achieved with and without long-term memory guidance.


Subject(s)
Memory, Short-Term/physiology , Models, Neurological , Visual Cortex/physiology , Visual Perception/physiology , Humans
6.
J Mol Biol ; 308(5): 993-1009, 2001 May 18.
Article in English | MEDLINE | ID: mdl-11352587

ABSTRACT

The determination by NMR of the solution structure of the phosphorylated enzyme IIB (P-IIB(Chb)) of the N,N'-diacetylchitobiose-specific phosphoenolpyruvate-dependent phosphotransferase system of Escherichia coli is presented. Most of the backbone and side-chain resonances were assigned using a variety of mostly heteronuclear NMR experiments. The remaining resonances were assigned with the help of the structure calculations.NOE-derived distance restraints were used in distance geometry calculations followed by molecular dynamics and simulated annealing protocols. In addition, combinations of ambiguous restraints were used to resolve ambiguities in the NOE assignments. By combining sets of ambiguous and unambiguous restraints into new ambiguous restraints, an error function was constructed that was less sensitive to information loss caused by assignment uncertainties. The final set of structures had a pairwise rmsd of 0.59 A and 1.16 A for the heavy atoms of the backbone and side-chains, respectively. Comparing the P-IIB(Chb) solution structure with the previously determined NMR and X-ray structures of the wild-type and the Cys10Ser mutant shows that significant differences between the structures are limited to the active-site region. The phosphoryl group at the active-site cysteine residue is surrounded by a loop formed by residues 10 through 16. NOE and chemical shift data suggest that the phosphoryl group makes hydrogen bonds with the backbone amide protons of residues 12 and 15. The binding mode of the phosphoryl group is very similar to that of the protein tyrosine phosphatases. The differences observed are in accordance with the presumption that IIB(Chb) has to be more resistant to hydrolysis than the protein tyrosine phosphatases. We propose a proton relay network by which a transfer occurs between the cysteine SH proton and the solvent via the hydroxyl group of Thr16.


Subject(s)
Cysteine/metabolism , Disaccharides/metabolism , Escherichia coli/enzymology , Nuclear Magnetic Resonance, Biomolecular , Phosphoenolpyruvate Sugar Phosphotransferase System/chemistry , Phosphoenolpyruvate Sugar Phosphotransferase System/metabolism , Binding Sites , Crystallography, X-Ray , Hydrogen Bonding , Models, Molecular , Mutation , Phosphoenolpyruvate Sugar Phosphotransferase System/genetics , Phosphorylation , Protein Structure, Secondary , Protons , Solvents , Substrate Specificity , Thermodynamics
7.
J Biol Chem ; 276(16): 12756-63, 2001 Apr 20.
Article in English | MEDLINE | ID: mdl-11278734

ABSTRACT

Part of the dimer and B/C domain interface of the Escherichia coli mannitol permease (EII(mtl)) has been identified by the generation of disulfide bridges in a single-cysteine EII(mtl), with only the activity linked Cys(384) in the B domain, and in a double-cysteine EII(mtl) with cysteines at positions 384 and 124 in the first cytoplasmic loop of the C domain. The disulfide bridges were formed in the enzyme in inside-out membrane vesicles and in the purified enzyme by oxidation with Cu(II)-(1,10-phenanthroline)(3), and they were visualized by SDS-polyacrylamide gel electrophoresis. Discrimination between possible disulfide bridges in the dimeric double-cysteine EII(mtl) was done by partial digestion of the protein and the formation of heterodimers, in which the cysteines were located either on different subunits or on one subunit. The disulfide bridges that were identified are an intersubunit Cys(384)-Cys(384), an intersubunit Cys(124)-Cys(124), an intersubunit Cys(384)-Cys(124), and an intrasubunit Cys(384)-Cys(124). The disulfide bridges between the B and C domain were observed with purified enzyme and confirmed by matrix-assisted laser desorption ionization-time of flight mass spectrometry. Mannitol did not influence the formation of the disulfide between Cys(384) and Cys(124). The close proximity of the two cysteines 124 was further confirmed with a separate C domain by oxidation with Cu(II)-(1,10-phenanthroline)(3) or by reactions with dimaleimides of different length. The data in combination with other work show that the first cytoplasmic loop around residue 124 is located at the dimer interface and involved in the interaction between the B and C domain.


Subject(s)
Cysteine , Escherichia coli/enzymology , Phosphoenolpyruvate Sugar Phosphotransferase System/chemistry , Phosphoenolpyruvate Sugar Phosphotransferase System/metabolism , Amino Acid Substitution , Binding Sites , Copper/pharmacology , Cross-Linking Reagents , Dimerization , Disulfides/analysis , Escherichia coli Proteins , Maleimides/pharmacology , Mannitol/metabolism , Monosaccharide Transport Proteins , Mutagenesis, Site-Directed , Oxidation-Reduction , Phenanthrolines/pharmacology , Phosphorylation , Recombinant Proteins/chemistry , Recombinant Proteins/metabolism , Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
9.
J Mol Biol ; 287(5): 845-51, 1999 Apr 16.
Article in English | MEDLINE | ID: mdl-10222194

ABSTRACT

The uptake of mannitol in Escherichia coli is controlled by the phosphoenolpyruvate dependent phosphotransferase system. Enzyme II mannitol (EIIMtl) is part of the phosphotransferase system and consists of three covalently bound domains. IICMtl, the integral membrane domain of EIIMtl, is responsible for mannitol transport across the cytoplasmic membrane. In order to understand this molecular process, two-dimensional crystals of IICMtl were grown by reconstitution into lipid bilayers and their structure was investigated by cryo-electron crystallography. The IICMtl crystals obey p22121 symmetry and have a unit cell of 125 Ax65 A, gamma=90 degrees. A projection structure was determined at 5 A resolution using both electron images and electron diffractograms. The unit cell contains two IICMtl dimers with a size of about 40 Ax90 A, which are oriented up and down in the crystal. Each monomer exhibits six domains of high density which most likely correspond to transmembrane alpha-helices and cytoplasmic loops.


Subject(s)
Crystallography/methods , Phosphoenolpyruvate Sugar Phosphotransferase System/chemistry , Cell Membrane , Crystallization , Escherichia coli Proteins , Freezing , Lipid Bilayers , Monosaccharide Transport Proteins , Protein Conformation
11.
J Biol Chem ; 273(33): 20785-94, 1998 Aug 14.
Article in English | MEDLINE | ID: mdl-9694823

ABSTRACT

The thermal stability and domain interactions in the mannitol transporter from Escherichia coli, enzyme IImtl, have been studied by differential scanning calorimetry. To this end, the wild type enzyme, IICBAmtl, as well as IICBmtl and IICmtl, were reconstituted into a dimyristoylphosphatidylcholine lipid bilayer. The changes in the gel to liquid crystalline transition of the lipid indicated that the protein was inserted into the membrane, disturbing a total of approximately 40 lipid molecules/protein molecule. The thermal unfolding profile of EIImtl exhibited three separate transitions, two of which were overlapping, that could be assigned to structural domains in the protein. Treatment with trypsin, resulting in the degradation of the water-soluble part of the enzyme while leaving the binding and translocation capability of the enzyme intact, resulted in a decrease of the Tm and enthalpy of unfolding of the membrane-embedded C domain. This effect was much more apparent in the presence of the substrate but only partly so in the presence of the substrate analog perseitol. These results are consistent with a recently proposed model (Meijberg, W., Schuurman-Wolters, G. K., and Robillard, G. T. (1998) J. Biol. Chem. 273, 7949-7946), in which the B domain takes part in the conformational changes during the substrate binding process.


Subject(s)
Escherichia coli/enzymology , Phosphoenolpyruvate Sugar Phosphotransferase System/metabolism , Base Sequence , Calorimetry, Differential Scanning , DNA Primers , Enzyme Stability , Escherichia coli Proteins , Mannitol/chemistry , Models, Chemical , Monosaccharide Transport Proteins , Phosphoenolpyruvate Sugar Phosphotransferase System/chemistry , Phosphorylation , Protein Conformation , Protein Folding , Substrate Specificity
12.
J Biol Chem ; 273(14): 7949-56, 1998 Apr 03.
Article in English | MEDLINE | ID: mdl-9525892

ABSTRACT

The transport across the cytoplasmic membrane and concomitant phosphorylation of mannitol in Escherichia coli is catalyzed by the mannitol-specific transport protein from the phosphoenolpyruvate-dependent phosphotransferase system, enzyme IImtl. Interactions between the cytoplasmic B and the membrane embedded C domain play an important role in the catalytic cycle of this enzyme, but the nature of this interaction is largely unknown. We have studied the thermodynamics of binding of (i) mannitol to enzyme IImtl, (ii) the substrate analog perseitol to enzyme IImtl, (iii) perseitol to phosphorylated enzyme IImtl, and (iv) mannitol to enzyme IImtl treated with trypsin to eliminate the cytoplasmic domains. Analysis of the heat capacity increment of these reactions showed that approximately 50-60 residues are involved in the binding of mannitol and perseitol, but far less in the phosphorylated state or after removal of the B domain. A model is proposed in which binding of mannitol leads to the formation of a contact interface between the two domains, either by folding of unstructured parts or by docking of preexisting surfaces, thus positioning the incoming mannitol close to the phosphorylation site on the B domain to facilitate the transfer of the phosphoryl group.


Subject(s)
Escherichia coli/enzymology , Phosphoenolpyruvate Sugar Phosphotransferase System/chemistry , Protein Conformation , Escherichia coli/chemistry , Escherichia coli Proteins , Monosaccharide Transport Proteins , Thermodynamics
13.
Cell Transplant ; 6(4): 403-12, 1997.
Article in English | MEDLINE | ID: mdl-9258514

ABSTRACT

To understand why class II Clostridium histolyticum collagenase is much more effective than class I in the isolation of rat pancreatic islets, we analyzed the role of these collagenases in pancreatic tissue dissociation. Crude collagenase was purified and then fractionated into class I and II with different enzyme activities and protein compositions. Pancreatic tissue was incubated with either class I, class II, or class I + II, with or without added protease, under conditions that eliminated endogenous proteolytic activity. The degradation of pancreatic extracellular matrix was monitored by selective histochemical staining of tissue samples. Class I and II showed similar capacities to degrade glycoproteins and degraded about one-third of the glycoproteins during 120 min of incubation. The degradation of collagens by class I and II was relatively more effective, 80 to 95% of the collagens being removed in 120 min, and also class dependent. Both in the presence and absence of protease, class II was more effective at degrading collagens than class I, but this difference in efficacy was less apparent than with islet isolation. Class I + II degraded collagens faster and more complete than did the individual classes, indicating a synergistic effect of class I and II. Evaluation of collagen degradation at various pancreatic locations did not show a selective degradation of collagens by any of the collagenase classes. The present data offer a partial explanation for the major role of class II in islet isolation.


Subject(s)
Cell Separation/methods , Clostridium/enzymology , Islets of Langerhans/pathology , Microbial Collagenase , Animals , Islets of Langerhans Transplantation , Male , Rats , Rats, Wistar , Sensitivity and Specificity
14.
Diabetologia ; 40(3): 262-70, 1997 Mar.
Article in English | MEDLINE | ID: mdl-9084963

ABSTRACT

Graft failure of alginate-polylysine microencapsulated islets is often interpreted as the consequence of a non-specific foreign body reaction against the microcapsules, initiated by impurities present in crude alginate. The aim of the present study was to investigate if purification of the alginate improves the biocompatibility of alginate-polylysine microcapsules. Alginate was purified by filtration, extraction and precipitation. Microcapsules prepared from crude or purified alginate were implanted in the peritoneal cavity of normoglycaemic AO-rats and retrieved at 1, 2, 3, 6, 9, and 12 months after implantation. With crude alginate, all capsules were overgrown within 1 month after implantation. With purified alginate, however, the portion of capsules overgrown was usually less than 10%, even at 12 months after implantation. All recipients of islet allografts in capsules prepared of purified alginate became normoglycaemic within 5 days after implantation, but hyperglycaemia reoccurred after 6 to 20 weeks. With intravenous and oral glucose tolerance test, all recipients had impaired glucose tolerance and insulin responses were virtually absent. After graft failure, capsules were retrieved (80-100%) by peritoneal lavage. Histologically, the percentage of overgrown capsules was usually less than 10% and maximally 31%. This small portion cannot explain the occurrence of graft failure. The immunoprotective properties of the capsules were confirmed by similar if not identical survival times of encapsulated islet allo- and isografts. Our results show that purification of the alginate improves the biocompatibility of alginate-polylysine microcapsules. Nevertheless, graft survival was still limited, most probably as a consequence of a lack of blood supply to the encapsulated islets.


Subject(s)
Alginates/standards , Biocompatible Materials , Diabetes Mellitus, Type 1/surgery , Graft Survival , Islets of Langerhans Transplantation/methods , Alginates/isolation & purification , Animals , Blood Glucose/metabolism , Capsules , Cell Separation/methods , Cells, Cultured , Diabetes Mellitus, Type 1/blood , Glucose Tolerance Test , Glucuronic Acid , Hexuronic Acids , Islets of Langerhans/cytology , Islets of Langerhans Transplantation/pathology , Islets of Langerhans Transplantation/physiology , Male , Polylysine/analogs & derivatives , Rats , Rats, Inbred BB , Rats, Inbred Lew , Rats, Inbred Strains , Time Factors , Transplantation, Homologous , Transplantation, Isogeneic
15.
Protein Sci ; 6(2): 304-14, 1997 Feb.
Article in English | MEDLINE | ID: mdl-9041631

ABSTRACT

The assignment of the side-chain NMR resonances and the determination of the three-dimensional solution structure of the C10S mutant of enzyme IIBcellobiose (IIBcel) of the phosphoenolpyruvate-dependent phosphotransferase system of Escherichia coli are presented. The side-chain resonances were assigned nearly completely using a variety of mostly heteronuclear NMR experiments, including HCCH-TOCSY, HCCH-COSY, and COCCH-TOCSY experiments as well as CBCACOHA, CBCA(CO)NH, and HBHA(CBCA)(CO)NH experiments. In order to obtain the three-dimensional structure, NOE data were collected from 15N-NOESY-HSQC, 13C-HSQC-NOESY, and 2D NOE experiments. The distance restraints derived from these NOE data were used in distance geometry calculations followed by molecular dynamics and simulated annealing protocols. In an iterative procedure, additional NOE assignments were derived from the calculated structures and new structures were calculated. The final set of structures, calculated with approximately 2000 unambiguous and ambiguous distance restraints, has an rms deviation of 1.1 A on C alpha atoms. IIBcel consists of a four stranded parallel beta-sheet, in the order 2134. The sheet is flanked with two and three alpha-helices on either side. Residue 10, a cysteine in the wild-type enzyme, which is phosphorylated during the catalytic cycle, is located at the end of the first beta-strand. A loop that is proposed to be involved in the binding of the phosphoryl-group follows the cysteine. The loop appears to be disordered in the unphosphorylated state.


Subject(s)
Escherichia coli/enzymology , Phosphoenolpyruvate Sugar Phosphotransferase System/chemistry , Amino Acid Sequence , Carbon Isotopes , Magnetic Resonance Spectroscopy , Molecular Sequence Data , Nitrogen Isotopes , Protons , Solutions
16.
Mem Cognit ; 25(6): 764-71, 1997 Nov.
Article in English | MEDLINE | ID: mdl-9421561

ABSTRACT

Effects of full and divided attention during study on explicit and implicit memory performance were investigated in two experiments. Study time was manipulated in a third experiment. Experiment 1 showed that both similar and dissociative effects can be found in the two kinds of memory test, depending on the difficulty of the concurrent tasks used in the divided-attention condition. In this experiment, however, standard implicit memory tests were used and contamination by explicit memory influences cannot be ruled out. Therefore, in Experiments 2 and 3 the process dissociation procedure was applied. Manipulations of attention during study and of study time clearly affected the controlled (explicit) memory component, but had no effect on the automatic (implicit) memory component. Theoretical implications of these findings are discussed.


Subject(s)
Attention , Memory , Adult , Humans , Learning , Mental Recall , Reference Values
17.
Mem Cognit ; 24(6): 766-76, 1996 Nov.
Article in English | MEDLINE | ID: mdl-8961821

ABSTRACT

Memory for words presented during general anesthesia was studied in two experiments. In Experiment 1, surgical patients (n = 80) undergoing elective procedures under general anesthesia were presented shortly before and during surgery with words via headphones. At the earliest convenient time after surgery (within 5 h) and 24 h later, memory was tested by asking patients to complete auditorily presented word stems with the first word that came to mind and to leave out words they remembered having heard earlier (exclusion task). Moreover, patients were requested to perform a "yes/no" forced-choice recognition task to assess recognition memory for both the pre- and intraoperative words. Memory for the material presented during anesthesia was demonstrated immediately after surgery and 24 h later by means of both tasks. In a second similar experiment (n = 80), the results were replicated. These findings show that anesthetized patients can process information that was presented intraoperatively.


Subject(s)
Anesthesia, General/psychology , Auditory Perception/drug effects , Memory/drug effects , Speech Perception/drug effects , Surgical Procedures, Operative/psychology , Unconsciousness/physiopathology , Unconsciousness/psychology , Verbal Learning/drug effects , Adolescent , Adult , Aged , Analysis of Variance , Chi-Square Distribution , Consciousness/physiology , Cues , Female , Free Association , Humans , Intraoperative Period/psychology , Male , Mental Recall/physiology , Middle Aged , Multivariate Analysis , Netherlands , Retention, Psychology/physiology , Word Association Tests
18.
Transplantation ; 62(7): 888-93, 1996 Oct 15.
Article in English | MEDLINE | ID: mdl-8878379

ABSTRACT

The observation that only a portion of all alginate-polylysine microcapsules are overgrown after implantation suggests that physical imperfections of individual capsules, rather than the chemical composition of the material applied, are responsible for inducing insufficient biocompatibility and thereby fibrotic overgrowth of those capsules. We recently developed a lectin binding assay that allows for quantifying the portion of inadequately encapsulated islets, and demonstrated that inadequately encapsulated islets induce a fibrotic response associated with graft failure. The present study investigates factors influencing the adequacy of encapsulation of pancreatic islets. We applied our lectin binding assay and found that the number of inadequate, and particularly incomplete, capsules is influenced by the following factors. (1) A capsule diameter of 800 micrometers is associated with a lower percentage of inadequate capsules than smaller (500 micrometers and 600 micrometers) or larger (1800 micrometers) capsules. (2) A high rather than low guluronic acid content of the alginate is associated with a lower percentage of inadequate capsules. This can be explained, at least in part, by smaller ranges of swelling and subsequent shrinkage during the encapsulation procedure. (3) An increase in viscosity caused by applying a higher alginate concentration compensates for a low guluronic acid content. This effect of increased viscosity cannot be explained by a reduced range of swelling and shrinkage during the encapsulation procedure. We conclude that alginates with a high guluronic acid content and a viscosity near the filtration limit are preferable in order to minimize the number of inadequate capsules.


Subject(s)
Alginates , Islets of Langerhans Transplantation/methods , Polylysine/analogs & derivatives , Animals , Capsules , Male , Particle Size , Rats , Rats, Wistar
19.
Biochemistry ; 35(8): 2759-66, 1996 Feb 27.
Article in English | MEDLINE | ID: mdl-8611583

ABSTRACT

Interdomain interactions in the mannitol-specific enzyme II of the phosphoenolpyruvate-dependent phosphotransferase system of Escherichia coli play a key role in the mechanism of mannitol transport across the membrane [Boer et al. (1995) Biochemistry 34, 3239-3247; Loikema et al. (1991) Biochemistry 30, 6716-6721]. In this study, we focus on the interaction between the hydrophilic A and B domains and try to determine those as a function of the phosphorylation state of the enzyme. To this end, unfolding studies on the subcloned domains IIAmtl and IIBmtl, as well as on the binary combination IIBAmtl, were performed, both in the unphosphorylated and in the phosphorylated states, using GuHCl and heat as the denaturant. It is shown that IIAmtl and IIBmtl, as well as P-IIAmtl and P-IIBmtl, unfold according to a two-state mechanism but that IIBAmtl and P2-IIBAmtl do not exhibit such behavior. Two transitions are observed instead, indicating a lack of strong positive cooperative interactions. DSC studies of the unphosphorylated proteins showed a destabilization of the B domain in IIBAmtl with respect to the free IIBmtl as indicated by a lowereing of the melting temperature and a lower enthalpy of unfolding. Furthermore, it is shown that phosphorylation has a destablilizing effect on both IIAmtl and IIBAmtl but not on IIBmtl. Possible explanations for this behavior and the biological relevance of the destabilizing forces in IIBAmtl are discussed.


Subject(s)
Escherichia coli/enzymology , Mannitol/metabolism , Phosphoenolpyruvate Sugar Phosphotransferase System/chemistry , Phosphoenolpyruvate Sugar Phosphotransferase System/metabolism , Binding Sites , Biological Transport, Active , Calorimetry, Differential Scanning , Escherichia coli Proteins , Hydrogen-Ion Concentration , Molecular Structure , Monosaccharide Transport Proteins , Phosphorylation , Protein Denaturation , Protein Folding , Recombinant Proteins/chemistry , Recombinant Proteins/metabolism , Thermodynamics
20.
Cell Transplant ; 4(6): 609-14, 1995.
Article in English | MEDLINE | ID: mdl-8714782

ABSTRACT

Because collagen is the major target in the enzymatic dissociation of the pancreas for islet isolation, we determined the amount of collagen and its distribution in a comparative study comprising normal pancreata of rat, dog, man, young pig, and adult pig. Collagen content was determined using a colorimetric method and its distribution was assessed in tissue sections stained with Sirius red. The collagen content is relatively low in the rat and adult pig pancreas, and the amount of collagen is relatively low in the septa of the rat and dog pancreas. Not the amount of collagen in the septa but collagen in the rest of the pancreas, mainly located between the acini, seems to determine the dissociation of the pancreatic tissue. This can be exemplified by the higher islet yields obtained from the adult vs. the young pig pancreas; the latter contains a higher total amount of collagen but a similar, relatively high, amount of collagen in the septa. A high amount of collagen surrounding the islets seems to be of secondary importance in islet isolations, because yields of the same magnitude are obtained from the canine and human pancreas containing a relatively low vs. high amount of collagen around the islets but a similar total collagen content. The rat pancreas contains both a low total amount of collagen and a high amount of collagen around the islets; therefore, the general experience that islet isolation procedures are effective in rats can be readily understood.


Subject(s)
Collagen/analysis , Islets of Langerhans/chemistry , Pancreas/chemistry , Animals , Cell Separation , Dogs , Humans , Islets of Langerhans/cytology , Male , Pancreas/ultrastructure , Rats , Swine
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