PubMed Health⌕ Search

Biomedical subjects

M Lemmers

Publications and source records attributed to M Lemmers.

10 recordsLinked to original sources
PubMed2006

Multiple shear-banding transitions in a supramolecular polymer solution.

We report on the nonlinear rheology of a reversible supramolecular polymer based on hydrogen bonding. The coupling between the flow-induced chain alignment and breakage and recombination of bonds between monomers leads to a very unusual flow behavior. Measured velocity profiles indicate three different shear-banding regimes upon increasing shear rate, each with different characteristics. While the first of these regimes has features of a mechanical instability, the second shear-banding regime is related to a shear-induced phase separation and the appearance of birefringent textures. The shear-induced phase itself becomes unstable at very high shear rates, giving rise to a third banding regime.

Biophysics↗
PubMed1996

MAG3 renal transplant tomography SPECT with a non-SPECT agent.

The authors encountered a renal transplant patient in whom tubular stasis permitted sufficient time to perform SPECT using Tc-99m MAG3. SPECT revealed a defect that was not apparent on the planar study. Renal biopsy showed acute vascular rejection. On a subsequent Tc-99m MAG3 SPECT study the defect had resolved.

Adult↗
PubMed1989

Renal adenocarcinoma with solitary metastasis to the contralateral adrenal gland: report of 2 cases and review of the literature.

We report 2 rare cases of renal adenocarcinoma with solitary metastasis to the contralateral adrenal gland, 1 recognized synchronously with the primary neoplasm and 1 found 15 years after nephrectomy. The latter case represents the longest reported interval between nephrectomy and treatment of a solitary contralateral adrenal metastasis of renal adenocarcinoma. Distinction of these metastatic tumors from primary adrenocortical carcinoma was facilitated by immunohistochemical markers. Twelve other reported cases of renal adenocarcinoma with solitary contralateral adrenal metastasis support aggressive surgical management of this lesion.

Adrenal Gland Neoplasms↗
PubMed1987

Mast cell involvement in interstitial cystitis.

A prospective study was designed to examine the relationship of mast cells, and eosinophilic leukocyte density and mediator levels to clinical and histological parameters of interstitial cystitis. Interstitial cystitis and control patients underwent bladder biopsy with histological examination, and quantification of intact and degranulated mast cell and eosinophilic leukocyte density. In addition, bladder tissue histamine content, urinary prostaglandin E2 excretion rates, and serum and urinary major basic protein levels were determined. A strong relationship among detrusor mast cell density, especially degranulated, and degree of epithelial loss, submucosal inflammation, epithelial ulceration, urinary pyuria and response to treatment was noted. Bladder tissue histamine content and urinary prostaglandin E2 excretion were increased in the interstitial cystitis patients. Eosinophil density in bladder biopsies was low uniformly, and interstitial cystitis and control patients showed no statistical difference. In addition, serum and urinary major basic protein levels were below the accepted normal lower limits for this protein. Therefore, our study demonstrates a relationship between the mast cell and the inflammatory process of interstitial cystitis. No similar relationship was noted for the eosinophil.

Biopsy↗
PubMed1984

The complete nucleotide sequence of the TL-DNA of the Agrobacterium tumefaciens plasmid pTiAch5.

We have determined the complete primary structure (13 637 bp) of the TL-region of Agrobacterium tumefaciens octopine plasmid pTiAch5 . This sequence comprises two small direct repeats which flank the TL-region at each extremity and are involved in the transfer and/or integration of this DNA segment in plants. TL-DNA specifies eight open-reading frames corresponding to experimentally identified transcripts in crown gall tumor tissue. The eight coding regions are not interrupted by intervening sequences and are separated from each other by AT-rich regions. Potential transcriptional control signals upstream of the 5' and 3' ends of all the transcribed regions resemble typical eukaryotic signals: (i) transcriptional initiation signals ('TATA' or Goldberg- Hogness box) are present upstream to the presumed translational start codons; (ii) ' CCAAT ' sequences are present upstream of the proposed 'TATA' box; (iii) polyadenylation signals are present in the 3'-untranslated regions. Furthermore, no Shine-Dalgarno sequences are present upstream of the presumed translational start codons.

Amino Acid Oxidoreductases↗
PubMed1982

Nucleotide sequence and transcript map of the Agrobacterium tumefaciens Ti plasmid-encoded octopine synthase gene.

We have determined the complete nucleotide sequence of the gene for the crown gall enzyme, octopine synthase. The sequence was derived from cloned fragments of the Agrobacterium tumefaciens Ti plasmid Ach5. It displayed a continuous open reading frame encoding a polypeptide chain of 358 amino acids. The nucleotide positions corresponding to the 5' end and poly(A) addition site of the mature octopine synthase mRNA from a tobacco tumor cell line were determined by S1 nuclease mapping. Two sequences closely resembling transcriptional control regions found in eukaryotic genes transcribed by RNA polymerase II were identified in the flanking genomic DNA: a sequence 5'-TATTTAAA-3' was located 32 base pairs upstream from the initiation site of transcription, and a hexanucleotide 5'-AATAAT-3' occurred 17 base pairs in front of the poly(A) addition site. No Shine-Dalgarno sequence was present in the untranslated 5' leader sequence. The observations indicate that this DNA sequence, although naturally carried by a bacterial plasmid, is programmed as a functional plant gene.

Amino Acid Oxidoreductases↗
PubMed1981

Further insight on the transferred-DNA of octopine crown gall.

Six octopine tumour lines incited by pTiB6S3, pTiAch5 and pTiA6 on tobacco, Arabidopsis and Petunia were studied by the Southern blotting hybridisation technique in order to define accurately the dimensions of the segments of plasmid origin transferred to the tumourous cell and their organisation in the plant genome. Emphasis has been put on the comparison between octopine and nopaline T-DNAs and on the lines presented here compared with those studied previously (Thomashow et al. 1980). The length of the transferred DNA segment does not depend on the plasmids used, nor on the host plants. The octopine T-DNA organisation in the cell nucleus is significantly different from that of nopaline T-DNAs: tandem arrangements of T-DNA segments could not be detected and the T-DNA itself is much shorter. The tumour lines described here can be compared to some extent with those studied by another group (Thomashow et al. 1980) by the same technique. However, some differences were observed. The transferred DNA was seen as a unique stretch of about 11 kb present only once per cell. No amplification of any part was noticed in any of these six lines. Examination of the restriction patterns presented by the boundary fragments of the T-DNA in these lines suggested that some of them were of common origin.

DNA Restriction Enzymes↗
PubMed1980

The interaction of Agrobacterium Ti-plasmid DNA and plant cells.

The tumour-inducing plasmids of Agrobacterium tumefaciens (Ti-plasmids) reveal several interesting properties. They are catabolic plasmids, which, instead of rendering Agrobacterium strains capable of catabolizing compounds found in Nature, force a plant to synthesize these catabolites (denoted 'opines'). This situation is obtained by insertion of a segment of the Ti-plasmid (the T-DNA) into the plant nucleus, where T-DNA genes become expressed and intervene in the biosynthesis of these opines. Cells containing the T-DNA behave as neoplasms (crown gall cells). Southern blotting shows that the insertion process responsible for T-DNA transfer probably recognizes special sequences on the T-DNA since the length of the T-DNA segment observed in different, independently isolated tumour lines was found to be similar. For the nopaline Ti-plasmids both left-hand and right-hand borders were found to be constant. For the octopine plasmid the left border was constant and at least two classes of right-hand borders were found. Upon redifferentiation of the transformed plant cells, the T-DNA was found to be conserved in all somatic cells examined. However, small deletions at the border fragments of the T-DNA have been observed. The exact arrangement and copy number of the T-DNA in a nucleus is still under study, but genomic cloning has already revealed that an interspersed tandem arrangement is dominant in nopaline tumours. Clones containing both the right border of one T-DNA and the left border of the neighbouring tandem T-DNA were isolated. In order to identify the different T-plasmid encoded functions an extensive use was made of transposon insertion mutagenesis. When an antibiotic resistance transposon was inserted into the non-essential regions of the T-DNA, a linked transfer to the plant DNA of the transposon together with the T-DNA was observed. This indicates that Ti-plasmids are possible vectors for genetic engineering in plants. A strategy is described for insertion of any cloned DNA segment into the T-DNA.

Amino Acids↗