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Biomedical subjects

F Müller

Publications and source records attributed to F Müller.

At least 199 records · Page 11Linked to original sources
PubMed1994

Ribosomal heterogeneity from chromatin diminution in Ascaris lumbricoides.

The genome of Ascaris lumbricoides encodes both germline- and soma-specific proteins homologous to the eukaryotic small ribosomal protein (Rp) S19. The two Ascaris homologs differ by 24 amino acid substitutions and are both components of the small ribosomal subunits. In oocytes, the germline RpS19 homolog (RpS19G) predominates. During chromatin diminution, however, the gene is eliminated from all presomatic cells, and RpS19G is replaced by the product of the somatic gene (RpS19S). Chromatin diminution in A. lumbricoides causes a change in the protein composition of ribosomes during development and represents an alternative means of gene regulation.

Amino Acid Sequence↗
PubMed1994

Replication of bovine papillomavirus type 1 origin-containing DNA in crude extracts and with purified proteins.

The in vitro replication of DNA containing the bovine papillomavirus (BPV-1) origin has been carried out with cell-free extracts from mouse FM3A and human HeLa cells. DNA synthesis required the E1 protein, the minimal origin of replication (nucleotides 7911-22 of the BPV-1 genome), and, at low levels of FM3A extract, the addition of the human single-stranded DNA-binding protein (also called RP-A or RF-A). The E2 protein was not absolutely required, but could stimulate DNA synthesis at low levels of E1. DNA synthesis was also reconstituted using purified proteins from HeLa cells. These protein factors included human single-stranded DNA-binding protein, topoisomerase I, and DNA polymerase (pol) alpha-primase complex. At low concentrations of pol alpha-primase complex, the formation of high molecular weight products was dependent on the addition of DNA polymerase delta holoenzyme containing proliferating cell nuclear antigen and activator 1, also called RF-C. We have overexpressed and isolated the E1 protein from bacteria. This protein also supported BPV DNA synthesis, both in crude extracts and with purified proteins suggesting that E1 phosphorylation is not required for BPV DNA replication in vitro.

Animals↗
PubMed1994

Cloning and functional expression of a cyclic-nucleotide-gated channel from mammalian sperm.

Cyclic nucleotide-gated (CNG) channels serve as downstream targets of signalling pathways in vertebrate photoreceptor cells and olfactory sensory neurons (see ref. 1 for review). Ca2+ ions that enter through CNG channels intimately control these signalling pathways by regulating synthesis or hydrolysis of cyclic nucleotides, and by decreasing ligand sensitivity of CNG channels. Several lines of evidence suggest that cyclic nucleotides and Ca2+ play important roles in chemotaxis of invertebrate sperm and fertilization (see ref. 9 for review), whereas their mechanisms of action in vertebrate sperm are largely unknown. Here we report the cloning and functional expression of a novel CNG channel from bovine testis. The channel polypeptide was functionally localized in sperm, but is also specifically expressed in cone photoreceptor cells. These channels might be involved in chemotaxis of sperm by controlling Ca2+ entry through a cyclic-nucleotide signalling pathway.

Amino Acid Sequence↗
PubMed1994

A single negative charge within the pore region of a cGMP-gated channel controls rectification, Ca2+ blockage, and ionic selectivity.

Ca2+ ions control the cGMP-gated channel of rod photoreceptor cells from the external and internal face. We studied ion selectivity and blockage by Ca2+ of wild-type and mutant channels in a heterologous expression system. External Ca2+ blocks the inward current at micromolar concentrations in a highly voltage-dependent manner. The blockage at negative membrane voltages shows a steep concentration dependence with a Hill coefficient of approximately 2. The blockage from the internal face requires approximately 1000-fold higher Ca2+ concentrations. Neutralization of a glutamate residue (E363) in the putative pore region between transmembrane segments H4 and H5 induces outward rectification and changes relative ion conductances but leaves relative ion permeabilities nearly unaffected. The current blockage at -80 mV requires approximately 2000-fold higher external Ca2+ concentrations and the voltage dependence is almost abolished. These results demonstrate that E363 represents a binding site for monovalent and divalent cations and resides in the pore lumen.

Amino Acid Sequence↗
PubMed1994

Neurulation in the normal human embryo.

The neural groove and folds are first seen during stage 8 (about 18 postovulatory days). Two days later (stage 9) the three main divisions of the brain, which are not cerebral vesicles, can be distinguished while the neural groove is still completely open. Two days later (stage 10) the neural folds begin to fuse near the junction between brain and spinal cord, when neural crest cells are arising mainly from the neural ectoderm. The rostral (or cephalic) neuropore closes within a few hours during stage 11 (about 24 days). The closure is bidirectional; it takes place from the dorsal and terminal lips and may occur in several areas simultaneously. The two lips, however, behave differently. The caudal neuropore takes a day to close during stage 12 (about 26 days) and the level of final closure is approximately at future somitic pair 31, which corresponds to the level of sacral vertebra 2. At stage 13 (4 weeks) the neural tube is normally completely closed. Secondary neurulation, which begins at stage 12, is the differentiation of the caudal part of the neural tube from the caudal eminence (or end-bud) without the intermediate phase of a neural plate.

Embryonic and Fetal Development↗
PubMed1994

Elevated serum levels of interleukin-4 and interleukin-6 in patients with common variable immunodeficiency (CVI) are associated with chronic immune activation and low numbers of CD4+ lymphocytes.

Serum immunoreactive interleukin (IL-)1 alpha, IL-4, IL-6 and tumor necrosis factor (TNF) alpha were measured in 42 patients with primary hypogammaglobulinemia (25 common variable immunodeficiency (CVI), 10 congenital hypogammaglobulinemia (CH), 7 X-linked agammaglobulinemia (XLA), and in 21 healthy controls. The cytokine levels were correlated to other immunological parameters including serum levels of neopterin and soluble CD8 (sCD8) antigen. IL-6 was detectable in 48% and IL-4 in 36% of the CVI patients, but in none of the controls. Seventy-five percent of the CVI patients with elevated IL-4 levels had detectable IL-6. In contrast, no patients in the XLA group and only three CH patients had detectable IL-4 or IL-6 levels. TNF alpha and IL-1 alpha were detected in only a few serum samples with no significant differences between patients and controls. In the CVI group elevated IL-6 levels were significantly associated to reduced numbers of CD4+ and CD19+ lymphocytes, elevated levels of neopterin and sCD8 antigen, and occurrence of splenomegaly and bronchiectasis. The raised IL-6 levels were confirmed in longitudinal testing, probably reflecting a characteristic immunological dysregulation in these patients. Cytokine alterations may play a role in the pathogenesis of the immunodeficiency and for the clinical manifestations in CVI patients. Alternatively, elevated cytokine levels may be only a marker of chronic immune activation, particularly in monocytes, possibly delineating a distinct subgroup of patients within the heterogeneous CVI group.

Adult↗
PubMed1994

Extremely stable transcripts may compensate for the elimination of the gene fert-1 from all Ascaris lumbricoides somatic cells.

The single-copy gene fert-1 becomes eliminated from all somatic cells during the process of chromatin diminution in Ascaris lumbricoides var. suum. By using Northern blot and in situ hybridization techniques, we have analyzed its rather unusual expression pattern. Different splicing and 3' end formation events generate in a developmentally regulated manner various poly(A)+ and poly(A)- fert-1 RNA species. The lack of any significant open reading frame in most of its RNA products indicates that fert-1 may function as structural RNA rather than encoding a protein. Fert-1 transcripts are produced in the precursors of the gametes, but degraded at the time of meiosis and not passed on to the zygote. Embryonic transcription of fert-1 sets in as soon as the female nucleus has completed its meiosis. Our data thus demonstrate that the Ascaris transcription apparatus is active prior to the general onset of zygotic transcription, which we think takes place in the four- to six-cell-stage embryos. Upon elimination of fert-1 gene from the somatic cells, most of its transcripts disappear. Two short fert-1 RNA products, however, are stably maintained throughout development until the second larval stage, which is more than 1 month after the elimination of their coding sequences. Possible functions of fert-1 are discussed.

Amino Acid Sequence↗
PubMed1994

Dyscoordination of pinch and lift forces during grasp in patients with cerebellar lesions.

Effects of cerebellar lesions on the production of isometric pinch force and the coordination of pinch and lift force were examined. Twenty-one patients, mostly with degenerative cerebellar disorders, and ten healthy controls lifted an instrumented test object using the precision grip of thumb and index finger. The load of the object could be varied to study the adaptation of pinch force generation. The results were: (1) Cerebellar patients were able to adapt their pinch force levels to the different object loads. (2) Patients showed a longer latency between the onset of pinch force and onset of life force than controls. The level of pinch force at the start of lift force was elevated. (3) Patients were able to use sensorimotor memory about object load to adapt force output based on previous experience through repetitive testing, but they were significantly less efficient than healthy controls. (4) The temporal profile of pinch force rate of change featured an irregular pattern characteristic for a lack of sufficient anticipatory parameterization.

Adolescent↗
PubMed1994

Localization of GABAA receptors in the rabbit retina.

The distribution of gamma-aminobutyric acidA (GABAA) receptors in the rabbit retina is investigated and compared with the distribution of GABAergic neurons using immunocytochemical methods. Antibodies against the alpha 1, beta 2/3, and gamma 2 subunits of the GABAA receptor label subpopulations of bipolar, amacrine and ganglion cells. Double labeling experiments show that the gamma 2 subunit is colocalized with the alpha 1 and the beta 2/3 subunits in bipolar, amacrine and ganglion cells. Electron microscopy reveals that in the outer plexiform layer, GABAA receptor immunoreactivity is present on dendrites of cone bipolar cells adjacent to the cone pedicles. Bipolar cell dendrites are also receptor-positive at synapses from interplexiform cells. Some receptor immunoreactivity is found intracellularly in processes of horizontal cells. In the inner plexiform layer, GABAA receptor immunoreactivity is present on both rod bipolar and cone bipolar axon terminals at putative GABAergic input sites. Amacrine and ganglion cell processes in sublamina a and b are also labeled.

Animals↗
PubMed1994

Rapid detection of cytomegalovirus infection in immunocompromised patients.

Several routinely employed diagnostic methods were analysed for their usefulness in aiding an early and rapid diagnosis of human cytomegalo-virus infection in immunocompromised patients. Clinical samples obtained during an 18-month period were examined by conventional culture, the shell vial method, detection of pp65 antigen and the polymerase chain reaction. Detection of pp65 antigen in peripheral leukocytes was the most useful method for rapid detection of infection at an early stage. Results of other rapid detection methods, the shell vial method and the polymerase chain reaction, gave useful support, while results obtained by conventional culture were not available until after the initiation of therapy. Only a small proportion of serological tests provided useful information for determining whether to treat the patient.

Antigens, Viral↗
PubMed1994

Impairments of precision grip in two patients with acute unilateral cerebellar lesions: a simple parametric test for clinical use.

A precision grip task was used to test two patients with acute unilateral cerebellar lesions due to a stroke and to compare performance of the affected and the unaffected hand. The results show, that grip force development is slowed and coordination of grip and lift force impaired by the lesion. Changes in shape and peak levels of grip force rate indicate a contribution of cerebellar function to the programming of precision grip. This method should be suited to monitor the course of cerebellar disease.

Cerebellar Diseases↗
PubMed1994

DNA-binding of androgen receptor overexpressed in mammalian cells.

In order to investigate the DNA-binding properties of the rat androgen receptor (rAR) in mammalian cells after addition of androgens and antiandrogens, we established a gel-shift assay with extract from COS-1 cells (CV-1 cells transformed with the DNA-tumour virus SV40) over-expressing the rAR. First, the rAR was overexpressed in COS-1 cells. Therefore the full-length AR cDNA was inserted immediately downstream from the SV40 early promoter of pECE to generate pECE-AR. Expression of the rAR driven by the SV40 early promoter yields constant and high levels of rAR protein. In addition, the vector contains the SV40 origin of replication for obtaining high copy vector numbers in COS-1 cells. The rAR-containing expression vector was transiently transfected into COS-1 cells using Transfectam Reagent, in order to achieve high transfection efficiency. Expression of biologically active receptor was tested by analyzing the effect of the synthetic androgen R1881 on induction of transiently transfected pMMTV-CAT. Steroid binding assays were carried out to confirm overexpression of biologically active AR and to determine the binding of different hormones and antihormones to AR in COS-1 cells transiently transfected with pECE-AR. Gel-shift experiments performed with whole cell extract of those cells, containing approximately 700 fmol AR/mg protein, and labeled AR-binding GRE (glucocorticoid responsive element) showed that R1881 induced the formation of a protein-GRE complex. Furthermore, the R1881-induced formation of the protein-GRE complex could be completed by addition of unlabeled excess of GRE but not of unspecific oligonucleotides, confirming sequence-specific binding of the R1881-induced protein-GRE complex.

Animals↗
PubMed1994

[Indications for the application of a high resolution coil in MR tomography].

This is the first study with high spatial resolution Magnetic Resonance Imaging (MRI), performed with a high resolution coil in a clinical whole-body system. Measurements were recorded with a slice thickness of 2 mm. A 256 x 256 matrix and a 2.5 cm field of view were used resulting in a pixel size of 0.01 mm2. MR images of the skin, hand, wrist, knee and ankle of 14 healthy volunteers, of three anatomic pathology tissue specimens and of three formalin-fixed specimens were obtained. Normal anatomy was identified and compared with the three gross anatomic pathology sections. The skin, hands, wrists and ankles of 30 patients were examined and a variety of pathological lesions were detected, including cutaneous neoplasms and ulceration, acute and chronic tendon lesions and pathologic features of the bone and wrist. Based on the excellent imaging of anatomic detail and superior contrast resolution, high resolution MRI proved an important complement for preoperative diagnosis.

Adult↗
PubMed1994

Serum levels of tumor necrosis factor-alpha (TNF alpha) and soluble TNF receptors in human immunodeficiency virus type 1 infection--correlations to clinical, immunologic, and virologic parameters.

Two EIAs (Medgenix and Quantikine) and a bioassay were used to measure tumor necrosis factor-alpha (TNF alpha) in serum samples from 73 human immunodeficiency virus type 1 (HIV-1)-seropositive patients and in samples from 2 control groups. All clinical groups of HIV-1-infected patients, regardless of concurrent illness, had significantly elevated levels of both types of soluble TNF receptors (sTNFRs) and immunoreactive TNF alpha (Medgenix EIA), with the highest concentrations among the AIDS patients. These TNF parameters were significantly correlated with reduced CD4+ lymphocyte counts. Only a few HIV-1-infected patients had detectable TNF alpha levels measured by the Quantikine EIA. TNF alpha bioactivity was significantly raised only in the AIDS group. Serially measured sTNFRs, expressed as sTNFR slopes, were significantly associated with survival in the patient group. The raised levels of immunoreactive TNF alpha and sTNFRs strongly indicate activation of the TNF alpha system during HIV-1 infection. Levels increase with disease progression and degree of immunodeficiency; thus, serially measured sTNFRs may give useful prognostic information in HIV-1 infection.

Adult↗
PubMed1994

Subnormal serum concentration of 1,25-vitamin D in human immunodeficiency virus infection: correlation with degree of immune deficiency and survival.

Vitamin D metabolites, immunologic, virologic, and clinical parameters, and survival time were determined in 22 asymptomatic human immunodeficiency virus (HIV)-infected patients (CDC stage II/III), 31 symptomatic HIV-infected patients (CDC stage IV), and 28 HIV-seronegative controls. Significantly lower serum levels of 1,25-vitamin D (1,25D) were found in symptomatic patients (median, 34 pg/mL; 25th-75th percentile, 21-45) compared with controls (49 pg/mL; 39-59) and asymptomatic patients (45 pg/mL; 42-50). In HIV-infected subjects, the serum level of 1,25D was positively correlated with CD4+ cell counts in peripheral blood (r = .35, P < .05) and negatively correlated with the level of serum neopterin (r = -.36, P < .01). HIV-infected patients with abnormally low 1,25D (< 25 pg/mL) also had shorter survival times than other HIV-infected subjects (P < .01). Low 1,25D levels did not appear to be related to vitamin D deficiency.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Enhanced generation of reactive oxygen species in monocytes from patients with common variable immunodeficiency.

Monocyte and macrophage dysfunction may be important for both immunopathogenesis and clinical manifestations in subgroups of patients with primary hypogammaglobulinaemia. In the present study we examined the ability to generate reactive oxygen species (ROS) in isolated monocytes from these patients by two different methods: superoxide dismutase (SOD) inhibitable cytochrome c reduction by O2- and nitroblue tetrazolium (NBT) reduction. Monocyte from patients with common variable immunodeficiency (CVI) demonstrated significantly enhanced ROS generation both unstimulated and stimulated (unopsonized zymosan and phorbol myristate acetate (PMA)). The enhanced oxidative burst response in CVI patients was found both with and without serum containing medium. Furthermore, serum from CVI patients did significantly enhance the oxidative burst response in monocytes from healthy blood donors compared with the effect of control serum. The enhanced ROS generation in CVI patients was significantly correlated with elevated serum levels of neopterin, reduced numbers of CD4+ lymphocytes in peripheral blood and occurrence of splenomegaly. In contrast to the CVI group, monocytes from patients with X-linked agammaglobulinaemia (XLA) did not show enhanced ROS generation. The increased oxidative burst response in monocytes from CVI patients most probably reflects in vivo activation of these cells. Our observations indicate the presence of a subgroup of CVI patients characterized by chronic immune activation particularly of monocytes. The enhanced ROS generation might be involved in immunopathogenesis (e.g. T cell dysfunction) and in the pathogenesis of clinical manifestations (e.g. malignancies and autoimmune disorders) in these patients.

Adult↗
PubMed1994

Hypothalamic-pituitary-thyroid axis in chronic alcoholism. II. Deiodinase activities and thyroid hormone concentrations in brain and peripheral tissues of rats chronically exposed to ethanol.

Thyroxine (T4), triiodothyronine (T3) concentrations, and the activities of the three deiodinase isoenzymes were measured in different brain regions and peripheral tissues of rats. According to an animal model of alcohol addiction, "behaviorally" dependent rats having lost control over their intake of ethanol were compared with alcohol-naive controls and ethanol-experienced, but "controlled" consumers. The two kinds of alcohol-experienced rats were investigated either 24 hr or 3 months after ethanol withdrawal. The results of these four groups were compared with those of an ethanol-naive control group. During withdrawal, the activities of type II 5'-deiodinase (which catalyzes deiodination of T4 and T3 in the CNS) in both the "behaviorally dependent" rats and the "controlled drinkers" were significantly lower than in the alcohol-naive controls in the frontal cortex, parieto-occipital cortex, hippocampus, and striatum, but not in the cerebellum or pituitary. Probably as a result, the tissue concentrations of T4 were higher in areas of the CNS in the groups exposed to alcohol. However, the T3 concentrations were normal. No relevant differences were seen between the activities of type III 5-deiodinase (which catalyzes the further deiodination of T3) observed in these groups. After 3 months of abstinence, the type II 5'-deiodinase activities had almost returned to normal in both "controlled drinkers" and "behaviorally dependent" animals, whereas type III 5-deiodinase activity was inhibited, possibly to maintain physiological concentrations of T3 during abstinence. Indeed, the tissue levels of T3 were normal in the areas of the CNS, and the T4 levels were still elevated. However, the liver concentrations of T3 and T4 were significantly lower in the "behaviourally dependent" animals than in the "controlled" drinkers after 3 months of abstinence, whereas no differences were found between the T4 and T3 concentrations in the areas of the CNS investigated in the two groups exposed to ethanol. These results suggest that chronic administration of ethanol affects intracellular thyroid hormone metabolism in both rat CNS and liver in the highly complex manner. No direct evidence of ethanol-induced enhancement of tissue uptake or concentrations was obtained. However, taking into account the numerous similarities between the clinical picture of hyperthyroidism and the symptomatology of alcoholism, it may be hypothesized that ethanol may directly influence any step in the as yet unknown biochemical cascade of thyroid hormone function.

Alcoholism↗