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Biomedical subjects

F Müller

Publications and source records attributed to F Müller.

At least 253 records · Page 14Linked to original sources
PubMed1992

[The microbial colonization of implant elements made of plastics and titanium].

12 edentate subjects wearing lower complete dentures stabilized by an IMZ-implant-supported Dolder bar took part in the experiment. Elastic (POM) and titanium connection parts were alternatingly inserted. After the removal of 24 POM and titanium elements from each of the patients, a qualitative analysis of the microbial flora was performed. Except for actinomycetes, aerobic as well as anaerobic microorganisms were found less frequently with titanium than with POM elements.

Actinomycetales↗
PubMed1991

New telomere formation after developmentally regulated chromosomal breakage during the process of chromatin diminution in Ascaris lumbricoides.

During the process of chromatin diminution, which takes place in all presomatic cells of the early Ascaris embryo, the heterochromatic termini of the chromosomes are lost. Here we show that the newly formed ends of the reduced somatic chromosomes carry tandem repeats of the telomeric sequence TTAGGC. Comparison of a cloned somatic telomere with the corresponding germline chromosomal region revealed that these telomeric repeats are not present at or near the chromosomal breakage site. They are most likely added by a telomerase-mediated event. Chromosomal breakage, which precedes the telomere addition process, takes place within a short, specific chromosomal region (CBR); however, it does not occur at a single locus, but rather at many different sites. Altogether, our data show that chromatin diminution in Ascaris is a complex molecular process that includes site-specific chromosomal breakage, new telomere formation, and DNA degradation.

Animals↗
PubMed1991

NMR studies on p-hydroxybenzoate hydroxylase from Pseudomonas fluorescens and salicylate hydroxylase from Pseudomonas putida.

p-Hydroxybenzoate hydroxylase from Pseudomonas fluorescens and salicylate hydroxylase from Pseudomonas putida have been reconstituted with 13C- and 15N-enriched FAD. The protein preparations were studied by 13C-NMR, 15N-NMR and 31P-NMR techniques in the oxidized and in the two-electron-reduced states. The chemical shift values are compared with those of free flavin in water or chloroform. It is shown that the pi electron distribution in oxidized free p-hydroxybenzoate hydroxylase is comparable to free flavin in water, and it is therefore suggested that the flavin ring is solvent accessible. Addition of substrate has a strong effect on several resonances, e.g. C2 and N5, which indicates that the flavin ring becomes shielded from solvent and also that a conformational change occurs involving the positive pole of an alpha-helix microdipole. In the reduced state, the flavin in p-hydroxybenzoate hydroxylase is bound in the anionic form, i.e. carrying a negative charge at N1. The flavin is bound in a more planar configuration than when free in solution. Upon binding of substrate the resonances of N1, C10a and N10 shift upfield. It is suggested that these upfield shifts are the result of a conformational change similar, but not identical, to the one observed in the oxidized state. The 13C chemical shifts of FAD bound to apo(salicylate hydroxylase) indicate that in the oxidized state the flavin ring is also fairly solvent accessible in the free enzyme. Addition of substrate has a strong effect on the hydrogen bond formed with O4 alpha. It is suggested that this is due to the exclusion of water from the active site by the binding of substrate. In the reduced state, the flavin is anionic. Addition of substrate forces the flavin ring to adopt a more planar configuration, i.e. a sp2-hybridized N5 atom and a slightly sp3-hybridized N10 atom. The NMR results are discussed in relation to the reaction catalyzed by the enzymes.

4-Hydroxybenzoate-3-Monooxygenase↗
PubMed1991

15N- and 13C-NMR investigations of glucose oxidase from Aspergillus niger.

The apoprotein of glucose oxidase from Aspergillus niger was reconstituted with specifically 15N- and 13C-enriched FAD derivatives and investigated by 15N- and 13C-NMR spectroscopy. On the basis of the 15N-NMR results it is suggested that, in the oxidized state of glucose oxidase, hydrogen bonds are formed to the N(3) and N(5) positions of the isoalloxazine system. The hydrogen bond to N(3) is more pronounced than that to N(5) as compared with the respective hydrogen bonds formed between FMN and water. The resonance position of N(10) indicates a small decrease in sp2 hybridization compared to free flavin in water. Apparently the isoalloxazine ring is not planar at this position in glucose oxidase. Additional hydrogen bonds at the carbonyl groups of the oxidized enzyme-bound FAD were derived from the 13C-NMR results. A strong downfield shift observed for the C(4a) resonance may be ascribed in part to the decrease in sp2 hybridization at the N(10) position and to the polarization of the carbonyl groups at C(2) and C(4). The polarization of the isoalloxazine ring in glucose oxidase is more similar to FMN in water than to that of tetraacetyl-riboflavin in apolar solvents. In the reduced enzyme the N(1) position is anionic at pH 5.6. The pKa is shifted to lower pH values by at least 1 owing to the interaction of the FAD with the apoprotein. As in the oxidized state of the enzyme, a hydrogen bond is also formed at the N(3) position of the reduced flavin. The N(5) and N(10) resonances of the enzyme-bound reduced FAD indicate a decrease in the sp2 character of these atoms as compared with that of reduced FMN in aqueous solution. Some of the 15N- and 13C-resonance positions of the enzyme-bound reduced cofactor are markedly pH-dependent. The pH dependence of the N(5) and C(10a) resonances indicates a decrease in sp2 hybridization of the N(5) atom with increasing pH of the enzyme solution.

Aspergillus niger↗
PubMed1991

Eliminated chromatin of Ascaris contains a gene that encodes a putative ribosomal protein.

Chromatin diminution in the nematodes Parascaris equorum and Ascaris lumbricoides leads to the formation of somatic cells that contain less DNA than the germ-line cells. We present molecular evidence for the coding potential of germ-line-specific DNA. We report on a cDNA clone that codes for a putative ribosomal protein (ALEP-1, for A. lumbricoides eliminated protein 1). That the corresponding gene is located in the eliminated portion of the genome indicates a difference in germ-line and somatic ribosomes of A. lumbricoides and P. equorum. Elimination of the ALEP-1 gene from all somatic cells in its fully active state may represent an alternative way to gene regulation.

Amino Acid Sequence↗
PubMed1991

Cloning and expression in vitro of a gene encoding tRNAArgACG from the nematode Caenorhabditis elegans.

A gene (rtr-1) coding for the tRNAArgACG has been isolated and characterized from the nematode, Caenorhabditis elegans. The coding portion is not interrupted by an intron and is followed by a track of four thymidines associated with termination by RNA polymerase III. The predicted mature product is 76 nucleotides (nt) long including the CCA tail, and is specific for the most used Arg codon in C. elegans. The gene can be transcribed and processed in a homologous in vitro system. The 82-nt primary transcript begins at the first purine upstream from the mature tRNA 5' end and terminates after the first thymidine of the terminator signal.

Animals↗
PubMed1991

Development of anencephaly and its variants.

Extreme variants of anencephaly in two human embryos of the same stage, namely 22 (54 days), shed new light on problems such as craniocerebral interrelationships and the timing of developmental events. Embryo X had a chondrocranium that possessed features typical of a holoacranial anencephalic skull and an extremely well-preserved brain, in which some of the neural tracts were comparable to those in a normal control. On the other hand, embryo Y of the same stage had a completely degenerated brain, although the chondrocranium was more nearly normal and represented the precursor of a meroacranial skull. A comparison of the two cases seems to indicate a certain independence between skull and brain. Moreover, it appears possible that the disturbances are related primarily to the skeletal, and only secondarily to the nervous, component. Comparisons with experimental data allow the conclusion that the maldevelopment involves mostly paraxial mesenchyme and little or no disturbance of neural crest. The timing of the mesenchymal defect is probably as early as stages 8 and 9 (18-20 days). This is also the time at which mesenchymal defects can result in failure of the neural tube to close.

Abnormalities, Multiple↗
PubMed1991

Characterization of products of TY1-mediated reverse transcription in Saccharomyces cerevisiae.

Transposition of the yeast transposable element, Ty, has been shown to require a reverse transcription process. By analysing the extrachromosomal Ty-specific nucleic acid molecules associated with overproduced Ty virus-like particles (Ty-VLPs), we identified several reverse transcribed cDNA strands. Most of them resemble the characteristic intermediates of the reverse transcription process described for authentic retroviruses: a (-) strong-stop DNA strand covalently bound to an RNA primer, two elongated (-) strands with one or two long terminal repeat (LTR) sequences and a (+) strong-stop DNA. Surprisingly, complete (+) strands and full-length linear duplex Ty DNA could not be detected. The structural features of two additional (+) strands may indicate some differences between the mechanisms of (+) strand synthesis in Ty and other retrotransposons or retroviruses.

Base Sequence↗
PubMed1991

Residual sensorimotor functions in a patient after right-sided hemispherectomy.

Sensorimotor functions were examined in a patient with left-sided infantile hemiparesis who underwent hemispherectomy (HS) on the right side at age 18 for intractable epilepsy. Pathological examination of the removed hemisphere showed a porencephalic cyst of the temporal lobe and of the frontoparietal operculum. On examination, the patient had hemianopia to the left and sensorimotor deficits only of the distal limbs contralateral to the HS. She walked with a barely perceptible limp. Axial and proximal movements were quasi normal, so that the patient could fully elevate both arms, flex and extend the forearm with nearly normal power and execute small, isolated precision movements of the arm around the shoulder joint. This astonishing proximal motor repertoire was mimicked on the somatosensory side where cutaneous sensation and kinesthesia were normal above the elbow and knee and contrasted the pronounced distal sensorimotor dysfunctions. Movement analysis by means of an optoelectronic two-camera position analysis system (Selspot II) showed normal flexion-extension synergies during gait, but abnormal synergic coupling between the shoulder and elbow joint during reaching and prehension. Distal movements were still possible but could only be performed as rigidly coupled movement synergies, such as closing and opening of the fist along with arm adduction/flexion or abduction/extension. She could engage these synergies for grasping and holding large objects. The performance of individual, fractionated finger movements was impossible. Involuntary mirror movements were elicited in both the affected and the normal arm, but with distinctly different phase relationships, indicating that different circuitries contribute to their generation. The case study reveals the existence of a bilaterally organized sensorimotor system that has the potential to provide quasi normal performance of the axial-proximal body parts on both sides. This raises the question why this potential cannot be better used in cases with only partial unilateral brain damage and persistent hemiplegia.

Arachnoid Cysts↗
PubMed1991

Assessment of cold induced alterations in catecholamine turnover of lean and glutamate-treated obese rats.

Excretion of norepinephrine (NE) and vanillylmandelic acid (VMA) in urine as well as NE-turnover in tissues from lean and glutamate-treated obese rats were determined in warm and cold environment. NE-and VMA-excretion in urine was elevated by cold exposure, indicating an activation of the sympathetic nervous system in animals of both groups. Organspecific NE-turnover responds with higher sensitivity to cold in obese rats but without complete compensation in brown adipose tissue. Urinary NE- and VMA- excretion as well as NE-turnover in organs confirmed that cold exposure activates the sympathetic nervous system. Measurement of NE-turnover in tissues gives organspecific information regarding alterations in sympathetic activity during cold exposure, whereas excretion of NE and VMA in urine is a summarizing measure for the whole body turnover only.

Adipose Tissue, Brown↗
PubMed1991

[Hyperbaric oxygen in the treatment of osteoradionecrosis of the mandible].

Osteoradionecrosis (ORN) of the mandible is one of the most dreaded complications in the treatment of cancer of the head and neck. If conservative and surgical treatment have not been successful, very often the only remaining solution is surgical intervention into the bone continuity of the mandible. In a group of eight patients suffering from ORN of the horizontal ramus of the lower jaw we gathered first experiences with hyperbaric oxygen therapy in combination with an operation to preserve the bone continuity (debridement of the bone and closing of the soft tissues). Hyperbaric oxygen was given during a time span of 13 to 52 hours (average: 36 hours). It was only with those two patients who received more than 50 hours of hyperbaric oxygen therapy that we achieved our aim of "total recovery from ORN of the mandible while saving its bone continuity". In one case where there was no clinically manifest recidivation of the tumour, the tumour showed rapid growth under hyperbaric oxygen therapy. In three cases partial resection of the mandible had to be performed without reconstruction for cure of ORN. Despite the loss of bone continuity these patients are only slightly cosmetically impaired and nutrition causes no problems. In two patients ORN still exists. On the basis of our first experiences with a small group of patients and in accordance with various publications, we conclude that hyperbaric oxygen therapy is a significant adjunct in the treatment of the mandible if a well-founded diagnosis is established and if it is followed by a well-adjusted therapy.

Adult↗
PubMed1991

Mapping eukaryotic replication origins in vivo by size analysis of purified nascent DNA strands.

A simple and efficient method for the mapping of eukaryotic replication origins was tested. The method is based on differential labeling of newly synthesized DNA with BrdUrd and subsequent separation of heavy nascent strands from parental DNA by conventional alkaline sucrose and neutral CsCl isopycnic gradient centrifugation. Purified nascent DNA is then size-fractionated on alkaline agarose gels and analyzed by sequential hybridization to specific probes of known location on the DNA segment of interest. Evaluation of the hybridization results allows: (i) determination of the direction of replication fork movement and (ii) location of the initiation site of DNA synthesis. Taking SV40 and polyoma virus as model systems, we demonstrate the feasibility of this procedure. It applicability to the location of chromosomal replication origins is discussed.

Blotting, Southern↗
PubMed1991

Both IgA subclasses are reduced in parotid saliva from patients with AIDS.

Secretory IgA (SIgA), the isotypes IgA1 and IgA2, and IgM were measured by ELISA in stimulated parotid saliva from patients with AIDS (n = 16), subjects with asymptomatic HIV infection (n = 28), and HIV-seronegative healthy controls (n = 19). SIgA was significantly reduced in the AIDS group (10.4 micrograms/ml) compared with the asymptomatic HIV-infected subjects (17.1 micrograms/ml) and the controls (23.0 micrograms/ml). This decrease comprised both IgA1 and IgA2 to a similar extent on a relative basis. The SIgA decrease in AIDS patients was in striking contrast to their serum IgA level, which was significantly increased (6.9 g/l) compared with the asymptomatic HIV-infected subjects (2.9 g/l) as well as the controls (2.8 g/l). Low parotid output of SIgA in patients with HIV infection was associated with low numbers of CD4+ lymphocytes in peripheral blood as well as the presence of oral infections. The parotid output of IgM was similar in all groups. A low level of SIgA in the external secretions of patients with AIDS may well contribute to their frequent mucosal infections of opportunistic microorganisms.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Cytokine response by human monocytes to Clostridium difficile toxin A and toxin B.

Clostridium difficile toxins A and B isolated from strain VPI 10463 were tested for induction of cytokine release by human monocytes. Toxin B at 10(-12) M activated human monocytes as measured by release of interleukin-1 (IL-1), tumor necrosis factor (TNF), or IL-6. These effects of toxin B were heat labile (51 degrees C, 30 min). Toxin B was as effective as bacterial lipopolysaccharides in inducing IL-1 beta but less effective in inducing TNF or IL-6. Toxin B and lipopolysaccharides were synergistic in induction of IL-1 beta, TNF, and IL-6. The toxin A preparation used was 1,000-fold less active than toxin B. Apart from the difference in activity, the two toxins showed identical patterns of reaction and there was no synergism between them. A short pulse with toxin B was sufficient to trigger IL-1 release. Toxin B was also extremely toxic for monocytes. The toxicity and the induced proinflammatory monokines (IL-1 and TNF) may contribute to the pathogenic mechanisms of C. difficile infection and pseudomembranous colitis.

Bacterial Proteins↗
PubMed1991

[Interactions between enterocytes and lymphocytes in the pathogenesis of celiac disease].

MHC antigens are positioned in the centre of the interactions between enterocytes and lymphocytes in the pathogenesis of coeliac disease. This disease is associated with the presence of specific alleles of MHC-class II genes. Class-II-gene products being present also on enterocytic membranes play an important role in the presentation of antigens and might lead in coeliac patients to an extraordinarily effective stimulation of CD4+ and/or CD8+ cells which induce damage to the intestinal epithelium by various mechanisms. Additionally so-called CD4-CD8-gamma/delta + lymphocytes might act cytotoxically on enterocytes. The typical HLA-haplotype, however, is found also in many healthy persons. Thus the presence of specific MHC molecules is not the only requirement for susceptibility to gliadins. Furthermore, a virus infection (cross reactivity with gliadins?) as an additional factor can not be considered to be sufficient for expression of coeliac disease. Results were presented demonstrating that gliadins affect undifferentiated enterocytes arguing for a role of additional enterocytic factors in the pathogenesis of the disorder. The findings suggest that gliadins interfere with late post-translational processes in the biosynthesis of sucrase-isomaltase. The integration of this effect into the pathogenetic mechanism of coeliac disease remains to be clarified.

CD4-Positive T-Lymphocytes↗
PubMed1991

[Early ultrasonic diagnosis of twins after insemination and contralateral embryo transfer in cattle and the results of calving].

In order to test the efficacy of ultrasonic diagnosis of early twin pregnancy, 20 dairy cows were inseminated, and 4-8 days later a seven-day old embryo was additionally transferred into the uterine horn contralateral to the site of ovulation. Sixteen of 20 cows became pregnant (80%). In 7 of 16 animals a twin pregnancy resulted (44%). Out of eight single pregnancies five (62.5%) followed insemination, and three (37.5%) followed egg transfer. Sixteen pregnant animals were examined ultrasonically. In 7 cases it was possible to estimate a twin pregnancy on the 41st day. This diagnosis was verified on parturition. The ultrasonically diagnosed side of pregnant horn in the singles was correct in 7 of 8 cases, identified by the genetical different origin of the offspring from artificial insemination or egg transfer.

Animals↗
PubMed1990

Tertiary structure of two-electron reduced Megasphaera elsdenii flavodoxin and some implications, as determined by two-dimensional 1H-NMR and restrained molecular dynamics.

The tertiary structure of the non-crystallizable two-electron-reduced Megasphaera elsdenii flavodoxin (15 kDa, 137 amino acid residues) has been determined using nuclear Overhauser enhancement restraints extracted from two-dimensional 1H-NMR spectra. A tertiary structure satisfying the experimental restraints very well (maximum NOE violation of 66 pm) was obtained with use of restrained molecular dynamics, using 509 distance restraints (including one non-NOE) on a starting structure modeled from the crystal structure of one-electron-reduced Clostridium MP flavodoxin. The protein consists of a central parallel beta-sheet surrounded on both sides by two alpha-helices. The flavin is positioned at the periphery of the molecule. The tertiary structure of the protein is highly defined with the exception of the flavin. The latter is expected to result from performing the restrained molecular dynamics simulation without water molecules and without proper charges on the flavin. The flavin, including the phosphate, the ribityl side chain and the isoalloxazine ring, is solvent accessible under the experimental conditions used and evidenced by a two-dimensional amide exchange experiment. This accessibility is expected to be important in the redox potential regulation of the semiquinone/hydroquinone couple of the protein. The amide exchange against deuterons and several typical line shapes in the two-dimensional NMR spectra are consistent with the structure generated. The structure is discussed in detail.

Bacterial Proteins↗