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Biomedical subjects

A Schlosser

Publications and source records attributed to A Schlosser.

At least 19 recordsLinked to original sources
PubMed2006

Microfibril-associated protein 4 binds to surfactant protein A (SP-A) and colocalizes with SP-A in the extracellular matrix of the lung.

Pulmonary surfactant protein A (SP-A) is an oligomeric collectin that recognizes lipid and carbohydrate moieties present on broad range of micro-organisms, and mediates microbial lysis and clearance. SP-A also modulates multiple immune-related functions including cytokine production and chemotaxis for phagocytes. Here we describe the molecular interaction between the extracellular matrix protein microfibril-associated protein 4 (MFAP4) and SP-A. MFAP4 is a collagen-binding molecule containing a C-terminal fibrinogen-like domain and a N-terminal located integrin-binding motif. We produced recombinant MFAP4 with a molecular mass of 36 and 66 kDa in the reduced and unreduced states respectively. Gel filtration chromatography and chemical crosslinking showed that MFAP4 forms oligomers of four dimers. We demonstrated calcium-dependent binding between MFAP4 and human SP-A1 and SP-A2. No binding was seen to recombinant SP-A composed of the neck region and carbohydrate recognition domain of SP-A indicating that the interaction between MFAP4 and SP-A is mediated via the collagen domain of SP-A. Monoclonal antibodies directed against MFAP4 and SP-A were used for immunohistochemical analysis, which demonstrates that the two molecules colocalize both on the elastic fibres in the interalveolar septum and in elastic lamina of pulmonary arteries of chronically inflamed lung tissue. We conclude, that MFAP4 interacts with SP-A via the collagen region in vitro, and that MFAP4 and SP-A colocates in different lung compartments indicating that the interaction may be operative in vivo.

Animals↗
PubMed2006

Skin biopsy findings and results of neuropsychological testing in the first confirmed cases of CADASIL in Norway.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is characterized by mutations in the notch3 gene. The mutation can be demonstrated by a gene test. The first group of Norwegian patients with CADASIL confirmed by gene testing was recently described. The present study includes six of the original nine patients with demonstrated notch3 mutation plus one patient with symptoms, who had been unwilling to go through gene testing. These seven patients underwent skin biopsy for electron microscopy. One patient was cognitively too impaired, but six went through neuropsychological testing. By electron microscopy characteristic granular osmiophilic material (GOM) was detected in all skin biopsies. The material is seen as granular deposits in the basal lamina of the smooth muscle layer, often making impressions upon adjacent smooth muscle cells. It seems important that blood vessels over a certain size (diameter >20 microm) are examined. A varying extent of cognitive decline was noted amongst all by neuropsychological testing. In cases with multiple infarctions reduction of perceptual speed, visuospatial skills and working memory could be demonstrated. Four patients showed executive dysfunction.

Adult↗
PubMed2001

Analysis of protein phosphorylation by a combination of elastase digestion and neutral loss tandem mass spectrometry.

Loss of phosphoric acid is the most effective fragmentation reaction of pSer- and pThr-containing phosphopeptides of small size (up to 10-15 residues) in low-energy collision-induced dissociation. Therefore, tandem mass spectrometry with neutral loss scanning was evaluated for its utility to analyze protein phosphorylation using protein kinase A (PKA) catalytic subunit, which is phosphorylated at Thr197 and Ser338, as an example. Analysis of tryptic digests of phosphoproteins by tandem mass spectrometry with scanning for neutral loss of phosphoric acid resulted in spectra with poor signal-to-noise ratio, mainly because of the large size of the phosphopeptides formed (>2 kDa). This unfavorable size was caused by the distribution of tryptic cleavage sites in PKA and by interference of phosphorylation with tryptic cleavage. To generate a set of smaller peptide fragments, digestion was performed using the low-specificity protease elastase. Analysis of the total elastase digest with neutral loss scanning resulted in observation of a set of partially overlapping phosphopeptides with high abundance, providing a complete coverage of PKA phosphorylation sites. The peptide size generated by elastase (0.5-1.5 kDa) is ideally suited for this scan mode, which was found to provide the highest specificity for detection of singly charged phosphopeptides (neutral loss of 98). Identification of the PKA phosphorylation sites was performed by mass spectrometric sequencing of the elastase-derived phosphopeptides, which provided highly informative product ion spectra.

Amino Acid Sequence↗
PubMed2001

Rapid tryptophan depletion plus a serotonin 1A agonist: competing effects on sleep in healthy men.

In the present study, we hypothesized that the REM-suppressing effects of 5-HT(1A) receptor stimulation would counteract the REM-disinhibiting effects of rapid tryptophan depletion (RTD), and vice versa. We administered RTD plus ipsapirone (10 mg, p.o.) or RTD plus placebo to 10 healthy men. In contrast to our previous findings but partially consistent with other studies, RTD in combination with placebo did not produce a significant enhancement of any REM sleep measure. The combination of RTD and ipsapirone produced a significant suppression of REM sleep that was remarkably similar to the effect of ipsapirone alone. These data appear to deepen the mystery of variable and inconsistent RTD-induced responses in healthy subjects. In the case of REM sleep measures, this differs markedly from the consistent RTD-induced REM-disinhibiting effect seen in medicated depressed patients.

Adult↗
PubMed2001

Ultradian rhythms of alternating cerebral hemispheric EEG dominance are coupled to rapid eye movement and non-rapid eye movement stage 4 sleep in humans.

Objective: To replicate the left minus right (L-R) hemisphere EEG power shifts coupled to rapid eye movement (REM) and non-rapid eye movement (NREM) sleep observed in 1972 by Goldstein (Physiol Behav (1972) 811), and to characterize the L-R EEG power spectra for total EEG, delta, theta, alpha and beta bands.Background: Ultradian alternating cerebral hemispheric dominance rhythms are observed using EEG during both waking and sleep, and with waking cognition. The question of whether this cerebral rhythm is coupled to the REM-NREM sleep cycle and the basic rest-activity cycle (BRAC) deserves attention.Methods: L-R EEG signals for ten young, normal adult males were converted to powers and the means were normalized, smoothed and subtracted. Sleep hypnograms were compared with L-R EEGs, and spectra were computed for C3, C4 and L-R EEG powers.Results: Significant peaks were found for all C3, C4 and L-R frequency bands at the 280-300, 75-125, 55-70 and 25-50 min bins, with power dominating in the 75-125 min bin. L-R EEG rhythms were observed for all bands. Greater right hemisphere EEG dominance was found during NREM stage 4 sleep, and greater left during REM for total EEG, delta and alpha bands (Chi-squares, P<0.001). Theta was similar, but not significant (P=0.163), and beta was equivocal.Conclusions: Earlier ultradian studies show that lateral EEG and L-R EEG power have a common pacemaker, or a mutually entrained pacemaker with the autonomic, cardiovascular, neuroendocrine and fuel-regulatory hormone systems. These results for L-R EEG coupling to sleep stages and multi-variate relations may present a new perspective for Kleitman's BRAC and for diagnosing variants of pathopsychophysiological states.

Journal Article↗
PubMed2001

Peri-marketing surveillance of lamotrigine in The Netherlands: doctors' and patients' viewpoints.

PURPOSE: Evaluation of daily clinical practice in prescribing lamotrigine in refractory epilepsy patients. METHODS: A collaborative, retrospective, peri-marketing study was performed in in- and out-patients attending one of the three Dutch epilepsy centres. Analysis of both patients' and doctors' information was performed in 520 patients using questionnaires and medical files. RESULTS: After one year of treatment 76% of patients maintained LTG treatment, an intention-to-treat analysis showed > = 50% seizure reduction in 23% of patients; 20-50% seizure reduction in 23% of patients. Six percent of patients became at least three months seizure free. In about 20% of patients seizures became less severe and shorter of duration, while in 6% an increase was found. After three months a significant decrease in number of concomitant antiepileptic drugs was found (change from mean 1.8 to 1.5 AEDs) (p = < 0.01). After twelve months the mean number of AEDs was 1.4 per patient. Overall percentage of side effects appeared to be significantly higher if patients' questionnaire data were used. Epilepsy patients considered side effects as an important factor in the choice of medication and in withdrawal of medication. Future developments of new AEDs should take this into account. CONCLUSION: This perimarketing study gives insight information about long-term daily use of lamotrigine, with emphasis on effectiveness. Patients complained in the questionnaires much more about side-effects, than was known according to the medical file. Therefore, it seems necessary to perform perimarketing studies more systematically.

Adolescent↗
PubMed2001

Fluorescence-monitored conformational change on the 3'-end of tRNA upon aminoacylation.

Fluorescent tRNAs species with formycine in the 3'-terminal position (tRNA-CCF) were derived from Escherichia coli tRNA(Val). Thermus thermophilus tRNA(Aap) and Thermus thermophilus tRNA(Phe). The fluorescence of formycine was used to monitor the conformational changes at the 3'-terminus of tRNA caused by aminoacylation and hydrolysis of aminoacyl residue from aminoacyl-tRNAs. An increase of about 15% in the fluorescence intensity was observed after aminoacylation of the three tRNA-CCF. This change in fluorescence amplitude that is reversed by hydrolysis of the aminoacyl residue, does not depend on the structure of the amino acid or tRNA sequence. A local conformational change at the 3'-terminal formycine probably involving a partial destacking of the base moiety in the ACCF end takes place as a consequence of aminoacylation. A structural change at the 3'-terminus of tRNA induced by attachment and detachment of the acyl residue may be important in controlling the substrate/product relationship in reactions in which tRNA participates during protein biosynthesis.

Chromatography, High Pressure Liquid↗
PubMed2001

Lack of association between carotid artery volume blood flow and cardiac output.

OBJECTIVE: The correlation of cardiac output and cerebral perfusion is unclear. We tested this potential association by correlating cardiac output data obtained by echocardiography and cerebral blood flow data as determined by color M-mode measurements of carotid artery blood flow. METHODS: We studied 43 patients with a broad spectrum of cardiac performance by means of transthoracic echocardiography. In these patients, different cardiac indices such as stroke volume, ejection fraction, and heart minute volume were determined. The data were correlated with volumetric flow measurements (color M-mode duplex system) of the common carotid arteries bilaterally. RESULTS: Heart minute volume ranged from 1.632 to 9.836 mL/min (mean +/- SD, 4.652 +/- 1.621 mL/min); ejection fraction ranged from 18% to 76% (mean, 48% +/- 16%). The relative fraction of carotid volume flow compared with heart minute volume was 15% +/- 6%. There was no correlation between ejection fraction, stroke volume, or heart minute volume and absolute volume flow in the carotid arteries when being adjusted for age. There was a highly significant inverse correlation (r = -0.8; P < .0001) of the relative fraction of the carotid volume flow (carotid volume flow/heart minute volume [percent]) and the heart minute volume. CONCLUSION: Our data support the concept that cerebral blood flow is independent of cardiac output.

Cardiac Output↗
PubMed2000

Five-membered ring formation in unimolecular reactions of peptides: a key structural element controlling low-energy collision-induced dissociation of peptides.

Unimolecular fragmentation reactions of peptides in low-energy collision-induced dissociation are reviewed in the mechanistic context of five-membered ring formation. This structure of intermediates or of fragment ions is recognized as a key element that governs unimolecular peptide fragmentation within the structural framework determined by the peptide backbone and its side-chains. A collection of collision-induced dissociation reactions is presented covering (i) b-ion formation, (ii) the fragmentation of N-terminally acylated peptides, (iii) neutral loss of the C-terminal amino acid in alkali or silver cationized peptides, (iv) the fragmentation of isoAsp-containing peptides and (v) the fragmentation of negatively charged Asp- or Glu-containing peptides. It appears that for all possible nucleophile-electrophile interactions leading to a five-membered ring structure an associated unimolecular peptide fragmentation reaction can be observed.

Amino Acid Sequence↗
PubMed2000

Analysis of isoaspartate in peptides by electrospray tandem mass spectrometry.

In view of the significance of Asn deamidation and Asp isomerization to isoAsp at certain sites for protein aging and turnover, it was desirable to challenge the extreme analytical power of electrospray tandem mass spectrometry (ESI-MS/MS) for the possibility of a site-specific detection of this posttranslational modification. For this purpose, synthetic L-Asp/L-isoAsp containing oligopeptide pairs were investigated by ESI-MS/MS and low-energy collision-induced dissociation (CID). Replacement of L-Asp by L-isoAsp resulted in the same kind of shifts for all 15 peptide pairs investigated: (1) the b/y intensity ratio of complementary b and y ions generated by cleavage of the (L-Asp/L-isoAsp)-X bond and of the X-(L-Asp/L-isoAsp) bond was decreased, and (2) the Asp immonium ion abundance at m/z 88 was also decreased. It is proposed that the isoAsp structure hampers the accepted mechanism of b-ion formation on both its N- and C-terminal side. The b/y ion intensity ratio and the relative immonium ion intensity vary considerably, depending on the peptide sequence, but the corresponding values are reproducible when recorded on the same instrument under identical instrumental settings. Thus, once the reference product ion spectra have been documented for a pair of synthetic peptides containing either L-Asp or L-isoAsp, these identify one or the other form. Characterization and relative quantification of L-Asp/L-isoAsp peptide mixtures are also possible as demonstrated for two sequences for which isoAsp formation has been described, namely myrG-D/isoD-AAAAK (deamidated peptide 1-7 of protein kinase A catalytic subunit) and VQ-D/isoD-GLR (deamidated peptide 41-46 of human procollagen alpha 1). Thus, the analytical procedures described may be helpful for the identification of suspected Asn deamidation and Asp isomerization sites in proteolytic digests of proteins.

Amino Acid Sequence↗
PubMed1999

Microfibril-associated protein 4 is present in lung washings and binds to the collagen region of lung surfactant protein D.

We have purified a glycoprotein from bovine lung washings using affinity chromatography on a maltose-affinity column. On SDS-polyacrylamide gel electrophoresis the protein showed a molecular mass of 36 kDa in the reduced state and 66 kDa in the unreduced state. On gel permeation chromatography the apparent molecular mass was 250 kDa. N-terminal sequencing showed homology to the human matrix protein microfibril-associated protein (hMFAP4), and the glycoprotein was designated bovine MFAP4 (bMFAP4). Lung surfactant protein D (SP-D) was also purified from lung washings, and calcium-dependent binding was demonstrated between bMFAP4 and SP-D. hMFAP4 was cloned, and recombinant hMFAP4 showed the same binding pattern to SP-D as bMFAP4. No binding was seen to recombinant SP-D composed of the neck region and carbohydrate recognition domain of SP-D, indicating that the interaction between MFAP4 and SP-D is mediated via the collagen region of SP-D. MFAP4 also showed calcium-dependent binding to mannan, which was partially inhibited by maltose. Our findings indicate that MFAP4 has two binding specificities, one for collagen and one for carbohydrate, and we suggest that MFAP4 may fix the collectins in the extracellular compartment during inflammation.

Amino Acid Sequence↗
PubMed1998

Amitogenic alginates: key to first clinical application of microencapsulation technology.

Microencapsulation refers to a technique of immunoisolation by coating single cells or tissue with a semipermeable membrane. By combining microencapsulation with a specific tissue culturing method, iso-, allo-, and xenotransplantation of parathyroid tissue has been achieved without immunosuppression in a long-term animal model. Prior to its clinical use, continued analyses of the alginate, used as a coating substance, determined its mitogenic properties. Purification of the commercially available alginate was achieved using patented electrophoretic procedures, resulting in an amitogenic alginate suitable for use in humans. However, this alginate exhibited entirely different physical properties. We have recently shown that isotransplanted parathyroid tissue remains vital and functioning in vivo over long periods of time using the novel amitogenic alginate. It is essential to document, whether the alginate is able to maintain immunoisolation. We have therefore assessed its in vivo function compared to the mitogenic alginate in a transgenic animal model. Altogether 600 parathyroid glands from 300 Lewis rats (donor animals) were excised and subjected to tissue culture. Thereafter they were allotransplanted to 30 parathyroidectomized Dark-Auita rats, microencapsulated with the amitogenic or the mitogenic alginate or naked, with 10 recipient animals in each group. Total serum calcium and parathyroid hormone levels were monitored continuously at weekly intervals for 30 weeks. After 26 weeks the transplant beds were excised and subjected to histologic examination. More than 6 months after allotransplantation 9 of 10 animals that had received amitogenic transplants, compared to 7 of 10 animals in the group with mitogenic microcapsules were normocalcemic. Animals that had received naked parathyroid tissue were hypocalcemic as soon as 2 weeks after allotransplantation. Correspondingly, normocalcemic animals showed vital parathyroid tissue inside the microcapsules, which were surrounded by a significantly smaller rim of fibroblasts when amitogenic alginate had been used. In addition to confirming physiologic long-term function, we were able to document for the first time that immunoisolation can also be achieved with the novel amitogenic alginate, which is suitable for clinical use.

Alginates↗
PubMed1998

[Heterologous transplantation of human parathyroid glands after microencapsulation with clinically suitable alginate : long-term function without immunosuppression in the animal model].

The role of parathyroid transplantation for the therapy of permanent hypoparathyroidism is undisputed. Because the parathyroid hormone deficiency syndromee rarely every is a vital thread to patients affected, systemic immunosuppression for transplant recipients is not justified. A technique of microencapsulation was modified for transplantation of parathyroid tissue. Using a core substance suitable for clinical use (amitogenic alginate), we accomplished allotransplantation of functioning parathyroid tissue in the long-term animal model and, very recently, reported first clinical cases without postoperative immunosuppression. In a controlled animal model of totally parathyroidectomized rats (PTX, two groups of n = 40), we investigated the ability of microencapsulation with the amitogenic alginate to enable transplantation across the highest immunological barrier (xenotransplantation: human-rat); to ensure intact transplant function and to protect from rejection. Rat parathyroid hormone (PTHRA i.S.) and serum calcium levels served as parameters of completeness of PTX; intact human PTH (PTHRA i.S.) and serum calcium levels of recipient animals were used to assess graft function. Also, tissue integrity within explanted capsules was assessed by histology. Cultured and microencapsulated parathyroid tissue resumes and maintains function in vivo, even if transplanted across the highest immunological barrier. Functionally, PTHHU i.S. replaced (PTHRA i.S.) in PTX animals entirely and restored normocalcemia. These results suggest, that xeno-transplantation of the parathyroids can be achieved without postoperative immuno-suppression in a long term animal model. These data also imply the possibility of clinical heterotransplantation of parathyroid glands.

Alginates↗
PubMed1997

Isotransplantation of microencapsulated parathyroid tissue in rats.

Permanent hypoparathyroidism is one of the most difficult of all endocrine disorders to treat medically. While autotransplantation of parathyroid tissue is clinically established, allotransplantation without immunosuppression is still at the level of animal experiments. Although persons affected by hypoparathyroidism are facing a clearly reduced quality of life, hypoparathyroidism rarely is a life threatening condition. Therefore, systemic immunosuppression for recipients of allotransplants is not justified. A conceptional alternative would be protecting the tissue to be transplanted from the immunologic response by coating it with a semipermeable membrane (microencapsulation). In 1994, we succeeded in iso-, allo- and xenotransplantation of microencapsulated parathyroid tissue in an animal model. Unfortunately, prior to the first clinical use, further analysis of the coating substance (alginate) demonstrated that it has mitogenic properties. Here, we report on the first successful transplantation of microencapsulated parathyroid tissue using a purified, non-mitogenic alginate which is suitable for clinical use.

Animals↗
PubMed1996

Transplantation of parathyroid tissue in experimental hypoparathyroidism: in vitro and in vivo function of parathyroid tissue microencapsulated with a novel amitogenic alginate.

Microencapsulation of tissues is an alternative to postoperative immunosuppression in transplantation. In 1994 iso-, allo- and xenotransplantation of microencapsulated parathyroid tissue was achieved in vivo. However, continued analysis of the coating substance (an alginate) determined mitogenic properties. Here, we report on the in vitro and in vivo function of parathyroid tissue microencapsulated with a novel amitogenic alginate suitable for use in humans. To assess in vitro function, parathyroid tissue encapsulated with mitogenic and amitogenic alginate was exposed to rising concentrations of calcium. For in vivo experiments, it was isotransplanted into parathyroidectomized rats. PTH release into medium and PTH serum levels as well as calcium levels of recipient rats were analyzed and compared to native (non-microencapsulated) tissue and empty capsules, respectively. In vivo, transplants were excised and subjected to histologic examination six months after trans-plantation. In vitro, parathyroid tissue encapsulated with amitogenic alginate releases approximately half of the PTH of the native tissue, not different from tissue encapsulated with the mitogenic alginate. In vivo, the novel alginate preserved parathyroid function similar to that of native tissue over the six month period resulting in complete reversal of hypoparathyroidism. Correspondingly, histologic examination revealed vital parathyroid tissue in intact microcapsules. By establishing in vitro function and successful long-term transplantation, we have documented the principle of microencapsulation of parathyroid tissue to be effective also with the novel amitogenic alginate, which is suitable for clinical use.

Alginates↗
PubMed1995

Reduced N-acetylaspartate content in the frontal part of the brain in patients with probable Alzheimer's disease.

The fully relaxed water signal was used as an internal standard in a STEAM experiment to calculate the concentrations of the metabolites: N-acetylaspartate (NAA), creatine + phosphocreatine [Cr + PCr], and choline-containing metabolites (Cho) in the frontal part of the brain in 12 patients with probable Alzheimer's disease. Eight age-matched healthy volunteers served as controls. Furthermore, T1 and T2 relaxation times of the metabolites and signal ratios: NAA/Cho, NAA/[Cr + PCr], and [Cr + PCr]/Cho at four different echo times (TE) and two different repetition times (TR) were calculated. The experiments were carried out using a Siemens Helicon SP 63/84 wholebody MR-scanner at 1.5 T. The concentration of NAA was significantly lower in the patients with probable Alzheimer's disease than in the healthy volunteers. No significant difference was found for any other metabolite concentration. For the signal ratios the only statistically significant difference was that the NAA/Cho ratio at TE = 92 ms and TR = 1.6 s was lower in the patients with probable Alzheimer's disease compared with the control group. A trend towards a longer T2 relaxation time for NAA in the patients with probable Alzheimer's disease than among the healthy volunteers was found, but no significant difference was found concerning the T1 and T2 relaxation times.

Aged↗