Biomedical subjects

J Hamming

Publications and source records attributed to J Hamming.

6 recordsLinked to original sources

PubMed2001

Irradiated versus nonirradiated endothelial cells: effect on proliferation of vascular smooth muscle cells.

PURPOSE: Endovascular radiation therapy is a promising strategy for the prevention of restenosis. Radiation prevents proliferation of vascular smooth muscle cells, thereby reducing the incidence of restenosis, but may also affect the remaining endothelial cells. For this reason, a comparison was made between irradiated and nonirradiated endothelial cells and their effects on the proliferation of vascular smooth muscle cells in a coculture system was evaluated. MATERIALS AND METHODS: A coculture system was used, in which both endothelial cells and vascular smooth muscle cells were grown on opposite sides of a semipermeable membrane. After a period of growth arrest, the proliferation of vascular smooth muscle cells was measured during four subsequent days. RESULTS: The presence of endothelial cells stimulated the proliferation of vascular smooth muscle cells during the first days of analysis but had an inhibitory effect during the subsequent days (P <.5). gamma-irradiation of endothelial cells resulted in a complete blockage of the proliferation of these cells. However, irradiated endothelial cells affected the proliferation of vascular smooth muscle cells in coculture in a fashion comparable to nonirradiated endothelial cells (P >.5). CONCLUSION: The results suggest that, in endovascular radiation therapy, irradiation of endothelial cells does not change their effects on the proliferative behavior of vascular smooth muscle cells.

Animals↗

PubMed1999

Complications in the endovascular repair of abdominal aortic aneurysms: a risk factor analysis.

OBJECTIVES: to identify risk factors for complications following endovascular repair of abdominal aortic aneurysms (AAAs). MATERIALS AND METHODS: endovascular AAA exclusion was attempted in 64 patients. Patient characteristics, anatomic features of the aneurysm, operative technical aspects, and the experience of the teams were correlated with mortality, occurrence of endoleak, and other complications. Perioperative complications were graded following the recommendations of the Ad Hoc Committee on reporting standards. For the assessment of correlation between risk factors and outcomes a logistic regression analysis was used. RESULTS: complications were observed in 43% of the procedures and were classified as mild (24%), moderate (55%) or severe (21%). American Society of Anaesthesiology (ASA) risk class 3 or 4, and advanced age were independent risk factors for perioperative death and complications. Adjuvant procedures or overstenting of the renal arteries with the uncovered part of the stent were not associated with increased risk of complications. Nevertheless, in four of 24 overstented renal orifices, a renal infarction or ischaemia of the kidney was observed on a postoperative CT scan. Advanced experience was associated with less complications, less endoleaks, and shorter operating time. CONCLUSIONS: high age and medical co-morbidity were associated with increased risk for perioperative complications and death. Additional perioperative procedures are usually well tolerated. With greater experience in endovascular AAA grafting the incidence of complications and endoleaks decreased.

Adult↗

PubMed1981

Electron microscopic analysis of transcription of a ribosomal RNA operon of E. coli.

Transcription in vitro of the E. coli ribosomal RNA operon, rrnE, was analysed by electron microscopy. The transcription initiation sites of the two rrnE promoters in tandem, P1 and P2, were mapped and the transcription from both sites was compared. The first and the second transcription initiation site are about equally used when all nucleotides are present at 200 microM. Lowering the concentration of the second promoter's start nucleotide CTP to 3 microM reduces the use of the P2 site sharply. At all CTP concentrations used the nascent RNA chains from P1 are in the average longer than those from P2 after a fixed transcription time. Most probably, this difference is caused by a longer average interval before formation of the productive complex with the second promoter.

Base Sequence↗

PubMed1980

E coli RNA polymerase-rRNA promoter interaction and the effect of ppGpp.

The interaction between RNA polymerase and the E coli r (ibosomal) RNA promoters of the rrnX and rrnE operon was studied with the filter-binding technique. Quantitative differences were observed between the rrnX and rrnE promoters: stable rrnX promoter complexes are formed faster, and are less sensitive towards heparin and salt than stable rrnE promoter complexes. The effect of ppGpp, the specific inhibitor of rRNA synthesis, on rrn promoter complex formation was studied. In the presence of ppGpp complexes are formed which cannot be trapped in a transcription complex by addition of the start nucleotides, and are therefore considered to be non-productive. A tentative mode for the action of ppGpp is proposed.

DNA Restriction Enzymes↗

PubMed1979

Interaction between RNA polymerase and a ribosomal RNA promoter of E. coli.

The interaction between RNA polymerase and the E. coli ribosomal (r) RNA promoter(s) of the rrnE operon has been studied by the filter-binding method. The extent of complex formation between RNA polymerase and rrnE promoter(s) is salt-dependent; ppGpp specifically inhibits interaction of RNA polymerase with the rrnE promoter(s). A tentative model is proposed for the molecular events in the early steps of rRNA initiation: a transition of the primarily formed, labile RNA polymerase-rRNA promoter complex to a more stable form is the determining step. This step is salt-sensitive; ppGpp acts on this "isomerization".

DNA-Directed RNA Polymerases↗

PubMedDate not supplied

Preoperative diagnostic tests for operable thyroid disease.

Although the availability and acceptance of fine-needle aspiration biopsy (FNAB) of thyroid nodules has increased, many physicians still use thyroid scintigraphy for distinguishing benign from malignant lesions. We evaluated these diagnostic tests in 350 patients who had thyroid surgery in our institution between 1977 and 1990. Histologic confirmation of FNAB was obtained in 265 patients. In the group of patients having surgery, 247 thyroid scintigraphies were performed. Our patients were divided into two groups (1977-1986 and 1986-1990). The first group comprised 173 patients with 173 FNABs and 126 scintigrams. The second group consisted of 177 patients having 92 FNABs and 121 scintigrams. Results of scintigrams were analyzed in the second group only. In 5 out of 120 cases where the FNAB result was "benign or probably benign" the lesion appeared to be malignant postoperatively. If the FNAB result was "malignant or probably malignant" (n = 83) the pathology report confirmed a malignancy in 68 cases (81.9%). In 56 instances of all 265 FNABs the cytology report was not conclusive ("uncertain"); in 21.4% of these cases a malignancy was found postoperatively. An FNAB-result "(probably) malignant" had a positive predictive value of 0.819 while the negative predictive value of a result "(probably) benign" is 0.950. An "uncertain" result does not take away our concern so this result should have the same consequences as those of a result "(probably) malignant". In that case, FNAB-sensitivity is 93.0% and specificity 66.1%. Eighty-five of the last 116 scintigraphies showed a solitary node. Eleven of these nodes were hot while 74 were cold.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗