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Biomedical subjects

G Mertens

Publications and source records attributed to G Mertens.

At least 37 records · Page 2Linked to original sources
PubMed1995

Heparan sulfate proteoglycans. Essential co-factors in receptor-mediated processes with relevance to the biology of the vascular wall.

Heparan sulfate (HS), a mixed bag of complex, heterogeneous and highly charged polysaccharides, is an essential co-factor in a large number of receptor-ligand interactions and cellular pathways. These co-factor functions depend on the binding-interactions of the HS chains with the ligand or receptor, or both. These binding interactions and the ensuing functional effects often depend on defined carbohydrate sequences within the HS chains, whereby the required sequences are not always represented within all natural forms of the polysaccharide. The proteins that are substituted with HS resort from a limited number of protein families, with different cellular, subcellular and supramolecular associations, and show differential activities in functional assays. It is likely that the natural co-factor functions of the HS proteoglycans depend on glycan-protein and protein-protein interactions that are subject to modulation, both at the glycan and protein levels.

Animals↗
PubMed1993

Detection of herpes simplex virus in the cerebrospinal fluid of patients with encephalitis using the polymerase chain reaction.

Herpes simplex encephalitis is a neurologic emergency demanding immediate institution of specific therapy in order to prevent mortality. Diagnosis, however, is a complex matter with controversy existing over the appropriateness of brain biopsy. We report the demonstration of herpes simplex virus DNA by means of the polymerase chain reaction (PRC) in the cerebrospinal fluid of 3 patients with herpes simplex encephalitis. One of the patients suffered from brain-stem encephalitis with high intensity signals in the pons on magnetic resonance imaging, the second reported case of this entity. The PCR for herpes simplex on a control series of cerebrospinal fluid of 20 patients with other central nervous system infections was negative. PCR of cerebrospinal fluid offers a sensitive, specific and rapid diagnosis of herpes simplex encephalitis, making brain biopsy unnecessary. Still, the importance of strict measures to prevent contamination cannot be stressed enough. It is possible that due to the high sensitivity of the PCR, herpes simplex may be found in other infectious syndromes of the central nervous system.

Adult↗
PubMed1992

Cell surface heparan sulfate proteoglycans from human vascular endothelial cells. Core protein characterization and antithrombin III binding properties.

Human aortic endothelial cells (HAEC) and human umbilical vein endothelial cells (HUVEC) were labeled with 35SO(4)2- for 48 h. The membrane-associated proteoglycans were solubilized from these monolayers with detergent and purified by ion-exchange chromatography on Mono Q, incorporation in liposomes, and gel filtration. The liposome-intercalated proteoglycans were 125I-iodinated and treated with heparitinase before SDS-polyacrylamide gel electrophoresis. Radio-labeled proteins with apparent molecular masses of 130, 60, 46, 35, and 30 kDa (HAEC) and 180, 130, 62, 43, and 35 kDa (HUVEC) were detected by autoradiography. Further characterization by affinity chromatography on immobilized monoclonal antibodies and by Northern blot analysis provided evidence for the expression of syndecan, glypican, and fibroglycan in human endothelial cells. Most of the heparan sulfate which accumulated in the subendothelial matrix was implanted on a 400-kDa core protein. This protein was immunologically related to perlecan and bound to fibronectin. Binding studies on immobilized antithrombin III suggested that all membrane-associated heparan sulfate proteoglycan forms had the capacity to bind to antithrombin III but that high affinity binding was more typical for glypican. Most of the proteoglycans isolated from the extracellular matrix also bound only with low affinity to antithrombin III. These results imply that glypican may specifically contribute to the antithrombotic properties of the vascular wall.

Antithrombin III↗
PubMed1992

[Pulmonary embolism: which diagnostic approach?].

The recent literature dealing with the diagnosis of pulmonary embolism is reviewed. Clinical signs, electrocardiogram and arterial blood gases analysis are not very helpful whereas a normal level of blood D-dimers makes the diagnosis of pulmonary embolism very unlikely. Lung scanning must be interpreted carefully in parallel with chest radiography. It is most useful if the pattern is either normal or of high probability. All intermediate scans are inconclusive and need a pulmonary arteriogram. Another option in patients with good cardiorespiratory reserve is the use of repeated non-invasive investigations of the lower limbs.

Blood Gas Analysis↗
PubMed1991

[The potentials and limits of percutaneous needle biopsy in the histological classification of malignant tumors].

180 sonographically guided percutaneous biopsies in a variety of anatomic regions (abdomen, 110; thorax, 33; neck, 28; breast, 4; extremity, 5) were retrospectively reviewed to evaluate the percentage of correct histologic diagnoses of malignant tumours. A positive diagnosis of malignancy was established in 101 (96%) of 107 malignant tumours. A correct histologic classification was achieved in 79 (73%) of 108 malignant tumours by means of cytologic and histologic examination of the tissue acquired. Correct histologic classification of malignant tumours depends on several factors including a) needle diameter, b) location of the tumour, c) clinical constellation and, most important d) the complexion of the tumour histology. The percentage of correct histological diagnoses varied between carcinomas (79%), Hodgkin lymphomas (100%), non-Hodgkin lymphomas (45%), sarcomas (50%) and carcinoid tumours (0%). Histological classification of malignant tumours by means of percutaneous biopsy can be improved by multiple biopsies of different portions of the tumour and by using larger cutting needles.

Adolescent↗
PubMed1988

Site-specific recombination in bacteriophage Mu: characterization of binding sites for the DNA invertase Gin.

Site-specific DNA inversion in phage Mu is catalysed by the phage-encoded DNA invertase Gin and a host factor FIS. We demonstrate that purified Gin protein binds specifically to 34-bp sequences that flank the G segment as inverted repeats. Each inverted repeat (IR) contains two binding sites for Gin which have to be arranged in a specific configuration to constitute a recombinogenic site. While one of these sites is bound when present alone, the other site is bound only in conjunction with the first one, suggesting cooperative binding. In addition to the sites within the IR, Gin binds with lower affinity to AT-rich sequences adjacent to the IR. We demonstrate that these sites do not participate in the inversion reaction. The IR itself can be shortened to 25 bp without effect on inversion frequency. Using gel mobility shift experiments on circular permuted fragments containing the IR we show that Gin bends DNA upon binding. We discuss the possibility that DNA bending is related to the formation of a productive synaptic complex.

Base Sequence↗
PubMed1988

The DNA invertase Gin of phage Mu: formation of a covalent complex with DNA via a phosphoserine at amino acid position 9.

The DNA invertase Gin encoded by bacteriophage Mu catalyses efficient site-specific recombination between inverted repeat sequences (IR) in vivo and in vitro in the presence of the host factor FIS and the recombinational enhancer. We demonstrate that Gin alone is able to introduce single strand breaks into duplex DNA fragments which contain the IR sequence. Strand cleavage is site-specific and can occur on either strand within the IR. Cleaved molecules contain Gin covalently attached to DNA. The covalent complex is formed through linkage of Gin to the 5' DNA phosphate at the site of the break via a phosphoserine. Extensive site-directed mutational analysis showed that all mutants altered at serine position 9 were completely recombination deficient in vivo and in vitro. The mutant proteins bind to DNA but lack topoisomerase activity and are unable to introduce nicks. This holds true even for a conservative amino acid substitution at position 9. We conclude that serine at position 9 is part of the catalytic domain of Gin. The intriguing finding that the DNA invertase Gin has the same catalytic center as the DNA resolvases that promote deletions without recombinational enhancer and host factor FIS is discussed.

Base Sequence↗
PubMed1987

The Brachmann-de Lange syndrome in two siblings of normal parents.

In this report we describe two male siblings with typical Brachmann-de Lange syndrome. Both presented a severe form of this MCA syndrome, and died at the age of 3 months and 3 weeks, respectively. Family history was completely negative, parents were normal, and prometaphase chromosome studies failed to reveal a chromosomal basis for this unique malformation syndrome.

Abnormalities, Multiple↗
PubMed1986

Purification and properties of the DNA invertase gin encoded by bacteriophage Mu.

The host range of bacteriophage Mu is regulated through an invertible segment. Inversion requires the presence of two properly oriented recombination sites and a recombinational enhancer sis. The reaction is catalyzed by the Mu-encoded DNA invertase Gin and a host factor termed factors for inversion stimulation (FISs). We present a novel purification scheme for Gin. Purified Gin alone catalyzes the inversion reaction at very low efficiency recombining less than 0.8% of substrate molecules. When supplemented with FIS substrates containing the recombinational enhancer are recombined efficiently. Stoichiometric amounts of Gin are required for recombination.

Cations, Divalent↗
PubMed1985

G inversion in bacteriophage Mu DNA is stimulated by a site within the invertase gene and a host factor.

The Gin function of bacteriophage Mu catalyzes inversion of the G DNA segment, thus switching the host range of Mu phage particles. This site-specific recombination event takes place between inverted repeat sequences (IR) that border the G segment. Sequences in the Mu beta region extending approximately from position 118 to 178 are essential for efficient inversion. In cis this region, termed sis, stimulates inversion about 15-fold. Neither the relative orientation of sis with respect to the IR sequences nor the distance to IR substantially influences the stimulatory effect. For full activity purified Gin protein must be supplemented with crude host factor from E. coli K12. We suggest that, in addition to Gin, a DNA-binding host protein is required for efficient G inversion.

Bacterial Proteins↗