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Biomedical subjects

F Müller

Publications and source records attributed to F Müller.

At least 343 records · Page 19Linked to original sources
PubMed1988

[Particle agglutination test: a new technic for the detection of HIV-1 antibodies].

Two techniques for detection of anti-HIV-1 antibodies were comparatively investigated. It is shown that the particle agglutination (PA) is at least equivalent to the enzyme immunoassay (EIA) as far as sensitivity is concerned. A ten-fold increased sensitivity of PA was found when compared with Western Blot results. Furthermore, the detection of specific IgM antibodies in sera of HIV-1-infected persons is possible when the PA is used. The high stability of PA reagents when stored at 37 degrees C, the simple performance of the assay, and the possibility of automatization are important advantages of the PA when compared with the EIA.

Acquired Immunodeficiency Syndrome↗
PubMed1988

[The Vesalius of human embryology].

Human embryology was founded 100 years ago by WILHELM HIS, who may rightly be called the "Vesalius of human embryology". 3 landmarks were published in Germany within a quarter of a century: The Anatomie menschlicher Embryonen of HIS, KEIBEL'S Normentafeln, and KEIBEL and MALL'S Handbuch der Entwicklungsgeschichte des Menschen. The staging of the human embryo, now associated with the names of STREETER and O'RAHILLY, was first proposed by MALL in Anatomischer Anzeiger.

Embryology↗
PubMed1987

Amacrine cells in the ganglion cell layer of the cat retina.

Following transection of the optic nerve, ganglion cells in the cat retina undergo retrograde degeneration. However, many small profiles (less than or equal to 10 micron) survive in the ganglion cell layer. Previously considered to be neuroglia, there is now substantial evidence that they are displaced amacrine cells. Their density increases from approximately 1,000 cells/mm2 in peripheral retina to 7,000 cells/mm2 in the central area. Their total number was found to be 850,000, which is five times the number of ganglion cells and also five times the number of astrocytes. Uptake of 3H-muscimol followed by autoradiography labelled 75% of the displaced amacrine cells; hence, the majority seem to be GABAergic. Immunocytochemistry with an antibody directed against choline-acetyl-transferase labelled approximately 10% of the displaced amacrines in the peripheral retina and 17% in the central area. Uptake of serotonin (5-HT) followed by immunocytochemistry was found in 25-30% of displaced amacrines. NADPH diaphorase histochemistry labelled approximately 5% of displaced amacrine cells. The sum of the various percentages make colocalization likely. Intracellular injection of Lucifer Yellow under microscopic control revealed that displaced amacrine cells constitute several morphological types.

Animals↗
PubMed1987

Type I-like intervening sequences are found in the rDNA of the nematode Ascaris lumbricoides.

The intervening sequences in the large ribosomal RNA gene of Ascaris lumbricoides var. suum show many similarities to the type I insertions, previously found only in some insect species. They include structural features, but also a presumed transcriptional inactivity in vivo: No transcript of the rDNA intervening sequence in A. lumbricoides could be detected in Northern and dot blot hybridizations. However, the primary structure of the Pol I promoter region is well conserved in interrupted and uninterrupted genes. Moreover, genes with an intervening sequence are correctly initiated in a whole-cell in vitro extract from Ascaris oogonia. Hence, the presence of the intervening sequence alone does not seem to account for a transcriptional inhibition in rRNA genes. As with the type I insertions of insect rDNA, some copies of the A. lumbricoides intervening sequence are also present in locations outside the rDNA cluster. About 50% of the extraribosomal copies are found in a repetitive sequence of the genome, and additional copies are inserted in unique sequences. These striking analogies to type I insertions are discussed, and lead to the conclusion that the two phenomena are undoubtedly related. This is the first report proving the presence of a type I-like insertion element outside of the class Insecta.

Animals↗
PubMed1987

Localization of the in vivo and in vitro transcription initiation site and comparative analysis of the flanking sequences in the two main size classes of Ascaris lumbricoides rDNA.

An accurate in vitro transcription system which utilizes the cloned 8.8 and 8.4 kb size classes of Ascaris rRNA genes (pAlr8 and pAlr13) and two kinds of cellular extracts from Ascaris oogonia has been established. Both rDNA containing plasmids are efficiently transcribed in vitro by RNA polymerase I from a unique site of rDNA which corresponds to the in vivo initiation site. The in vitro transcription product has a triphosphorylated 5'-end and starts on a G localized 414 bp (pAlr8) upstream of the beginning of the mature 18S rRNA. The promoter region has been delimited by testing the in vitro template activity of a series of restriction fragments. The region essential for the accuracy of initiation is contained within nucleotides -72 to +65, but full efficiency of transcription requires the additional presence of the region from nucleotides +66 to +84. The sequences upstream from position -72 do not appear to modulate the efficiency of specific in vitro initiation. Furthermore, the sequences flanking the transcription initiation site from position -1500 to +570 have been determined in the two cloned representatives of the two rDNA main size classes.

Animals↗
PubMed1987

The elucidation of the microheterogeneity of highly purified p-hydroxybenzoate hydroxylase from Pseudomonas fluorescens by various biochemical techniques.

Highly purified p-hydroxybenzoate hydroxylase from Pseudomonas fluorescens can be separated into at least five fractions by anion-exchange chromatography. All fractions exhibit the same specific activity and the enzyme exists mainly in the dimeric form in solution. Sodium dodecyl sulfate/polyacrylamide gel electrophoresis of a mixture of the different fractions reveals two apparent forms of enzyme molecules, while isoelectric focusing experiments, on the other hand, reveal six apparently different forms of enzyme molecules. It is shown that the different forms of enzyme molecules are due to the (partial) oxidation of Cys-116 in the sequence of the enzyme. This interpretation of the data is supported by kinetic measurements of the formation of hybrid dimeric molecules monitored by fast protein liquid chromatography, using purified enzyme containing Cys-116 either in the native and or the fully oxidized (sulfonic acid) state. By chemical modification studies using maleimide derivatives, 5,5'-dithiobis(2-nitrobenzoate) and H2O2, it is shown that sulfenic, sulfinic and sulfonic acid derivatives of Cys-116 are products of oxidation. The results are briefly discussed with respect to the possibility that this isolation artifact might also be partially responsible for the appearance of multiple forms of enzyme molecules in other biochemical preparations.

4-Hydroxybenzoate-3-Monooxygenase↗
PubMed1987

Structure and transcription termination of a lysine tRNA gene from Xenopus laevis.

Termination of RNA polymerase III transcripts commonly occurs at clusters of T residues. A T4 tract located 72 base-pairs beyond a lysine tRNA gene from Xenopus laevis serves as an efficient termination site for the tRNA(Lys) precursors synthesized from this gene in homologous cell-free extracts. Nucleotides following this T tract influence the extent of read-through transcription in vitro, but in a way that differs from Xenopus 5 S RNA termination. Only approximately 50% of the transcripts initiated in vitro extend as far as this downstream T cluster. The remainder prematurely terminate at a second T4 tract located within the gene itself. The contrasting behaviour of these two T tracts in injected oocytes indicates that termination can be influenced by more than just RNA polymerase III alone, and that different components may contribute to, or hinder, termination at these sites. Prematurely terminated tRNA(Lys) transcripts are detectable in RNA from ovary tissue but not from a kidney cell line, suggesting that read-through transcription beyond intragenic T clusters can be modulated in vivo.

Animals↗
PubMed1987

[Pleural empyema due to Streptococcus milleri].

Thus far little attention has been focused on the precise identification of Streptococcus viridans to species level and the clinical relevance of Streptococcus milleri, yet there is growing evidence that closer identification would be of significant clinical value. Streptococcus milleri was identified in 142 isolates from approximately 120 patients over a period of 12 months (June 1984-May 1985) at the Institute of Medical Microbiology, Zurich University Hospital. Pleural empyema was the source in eleven patients (10%). The presentation of six cases of pleural empyema in which Streptococcus milleri played a role, together with a review of the literature, may serve to emphasize the importance of an organism whose taxonomic status is still unclear.

Adult↗
PubMed1987

Chemical modification of arginine residues in p-hydroxybenzoate hydroxylase from Pseudomonas fluorescens: a kinetic and fluorescence study.

The flavoprotein p-hydroxybenzoate hydroxylase from Pseudomonas fluorescens was modified by several arginine-specific reagents. Modifications by 2,3-butanedione led to the loss of activity of the enzyme, but the binding of p-hydroxybenzoate and NADPH to the enzyme was little or not at all affected. However the formation of the enzyme-substrate complex of the modified enzyme was accompanied by an increase of the fluorescence of protein-bound FAD, in contrast to that of native enzyme which leads to quenching of the fluorescence. Enzyme modified by phenylglyoxal did not bind p-hydroxybenzoate nor NADPH. Quantification and protection experiments showed that two arginine residues are essential and a model is described which accounts for the results. Modification by 4-hydroxy-3-nitrophenylglyoxal reduced the affinity of the enzyme for the substrate and NADPH. The ligands offered no protection against inactivation. From this it is concluded that one arginine residue is essential at some stage of the catalysis. This residue is not associated with the substrate- or NADPH-binding site of the enzyme. Time-resolved fluorescence studies showed that the average fluorescence lifetime and the mobility of protein-bound FAD are affected by modification of the enzyme.

4-Hydroxybenzoate-3-Monooxygenase↗
PubMed1987

Computer ranking of the sequence of appearance of 73 features of the brain and related structures in staged human embryos during the sixth week of development.

The sequence of events in the development of the brain in human embryos, already published for stages 8-15, is here continued for stages 16 and 17. With the aid of a computerized bubble-sort algorithm, 71 individual embryos were ranked in ascending order of the features present. Whereas these numbered 100 in the previous study, the increasing structural complexity gave 27 new features in the two stages now under investigation. The chief characteristics of stage 16 (approximately 37 postovulatory days) are protruding basal nuclei, the caudal olfactory elevation (olfactory tubercle), the tectobulbar tracts, and ascending fibers to the cerebellum. The main features of stage 17 (approximately 41 postovulatory days) are the cortical nucleus of the amygdaloid body, an intermediate layer in the tectum mesencephali, the posterior commissure, and the habenulo-interpeduncular tract. In addition, a typical feature at stage 17 is the crescentic shape of the lens cavity.

Brain↗
PubMed1987

The development of the human brain, the closure of the caudal neuropore, and the beginning of secondary neurulation at stage 12.

Twenty-four embryos of stage 12 (26 days) were studied in detail and graphic reconstructions of five of them were prepared. The characteristic features of this stage are 21-29 pairs of somites, incipient or complete closure of the caudal neuropore, and the appearance of upper limb buds. The caudal neuropore closes during stage 12, generally when 25 somitic pairs are present. The site of final closure is at the level of future somite 31, which corresponds to the second sacral vertebral level. Non-closure of the neuropore may be important in the genesis of spina bifida aperta at low levels. The primitive streak probably persists until the caudal neuropore closes, when it is replaced by the caudal eminence or end-bud (Endwulst oder Rumpfknospe). The caudal eminence, which appears at stage 9, gives rise inter alia to hindgut, notochord, caudal somites, and the neural cord. The material for somites 30-34 (which appear in stage 13) is laid down during stage 12, and its absence would be expected to result in sacral agenesis. Aplasia of the caudal eminence results in cloacal deficiency and various degrees of symmelia. The junction of primary and secondary development (primäre und sekundäre Körperentwicklung) is probably at the site of final closure of the caudal neuropore. Secondary neurulation begins during stage 12. The cavity of the already formed spinal cord extends into the neural cord, and isolated spaces are not found within the neural cord. Primary and secondary neurulation are probably coextensive with primary and secondary development of the body, respectively. The telencephalon medium has enlarged, two mesencephalic segments (M1 and M2) are distinguishable, and rhombomere 4 is reduced. The sulcus limitans is detectable in the spinal cord and hindbrain (RhD), and in the mesencephalon and diencephalon, where it extends as far rostrally as the optic sulcus in D1. A marginal layer is appearing in the rhombencephalon and mesencephalon. The first nerve fibres are differentiating, chiefly within the hindbrain (from the nucleus of the lateral longitudinal tract). Optic neural crest is at its maximum, and the otic vesicle is giving crest cells to ganglion 7/8. Neural crest continues to develop in the brain and contributes to cranial ganglia 5, 7/8, and 10/11. The spinal crest extends as far caudally as somites 18-19 but shows no subdivision into ganglia yet. Placodal contribution to the trigeminal ganglion is not certain at stage 12. Such a contribution to ganglion 7/8 is not unlikely.(ABSTRACT TRUNCATED AT 400 WORDS)

Brain↗
PubMed1987

Processing of TY1 proteins and formation of Ty1 virus-like particles in Saccharomyces cerevisiae.

We have analysed functional properties of putative proteins encoded by the yeast transposable element, Ty1, by overexpression of TY genes. High-level expression was achieved by appropriate fusion of a Ty sequence, TY9C, to the yeast ADH1 promoter and transformation of yeast cells with this construction. As shown recently by others (Garfinkel et al. 1985; Mellor et al. 1985c) TY overexpression leads to an increase in particle-bound reverse transcriptase activity and to an intracellular accumulation of virus-like particles (Ty-VLPs). We have used a number of deletions in the second open reading frame (TYB) to identify functional domains required for processing and assembly of Ty proteins. Deletions in the TYB region with homology to acid proteases result in overproduction of an unprocessed form of the TYA protein (pro-TYA) which represents the major protein of Ty-VLPs. One particular mutant construction, TY9C-delta 36, led to the accumulation of a particle-bound, 160 kDa protein which cross-reacted with a mouse antiserum raised against purified pro-TYA protein. This supports the hypothesis that TYB is expressed as a TYA/TYB fusion protein which is processed by a TYB-encoded protease activity. Ty-VLPs are formed in the absence of protein processing and even when the TYB gene is not expressed. Thus, we assume that the assembly of Ty particles occurs prior to processing of Ty proteins.

DNA Restriction Enzymes↗
PubMed1987

In situ hybridization analysis of cytomegalovirus lytic infection in Kaposi's sarcoma associated with AIDS. A study of 14 autopsy cases.

Cytomegalovirus (CMV) was assayed by in situ hybridization with commercially available biotin-labeled CMV-DNA probes in 45 formalin-fixed paraffin-embedded autopsy specimens with Kaposi's sarcoma from 14 cases of the acquired immune deficiency syndrome (AIDS). In seven of the 14 cases, a few scattered hybridizing cells were detected in Kaposi's sarcoma, but not all specimens from the same case showed such cells. Most of the positive cells were peculiarly swollen and not typical of Kaposi's sarcoma cells. All positive cases had at least some CMV-infected organs with typical cytomegalic cells containing nuclear inclusions while five of the 7 negative cases revealed no CMV-infected tissue by conventional light microscopy. Our results suggest that this in situ hybridization procedure using biotin-labeled DNA probes only reveals generalized CMV infection that is a consequence of impairment of immune mechanisms in AIDS patients.

Acquired Immunodeficiency Syndrome↗