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D Sievers

Publications and source records attributed to D Sievers.

7 recordsLinked to original sources
PubMed1999

The antisense sequence of the HIV-1 TAR stem-loop structure covalently linked to the hairpin ribozyme enhances its catalytic activity against two artificial substrates.

This work is an in vitro study of the efficiency of catalytic antisense RNAs whose catalytic domain is the wild-type sequence of the hairpin ribozyme, derived from the minus strand of the tobacco ringspot virus satellite RNA. The sequence in the target RNA recognized by the antisense molecule was the stem-loop structure of the human immunodeficiency virus-1 (HIV-1) TAR region. This region was able to form a complex with its antisense RNA with a binding rate of 2 x 10(4) M(-1)s(-1). Any deletion of the antisense RNA comprising nucleotides of the stem-loop resulted in a decrease in binding rate. Sequences 3' of the stem in the sense RNA also contributed to binding. This stem-loop TAR-antisense segment, covalently linked to a hairpin ribozyme, enhanced its catalytic activity. The highest cleavage rate was obtained when the stem-loop structure was present in both ribozyme and substrate RNAs and they were complementary. Similarly, an extension at the 5'-end of the hairpin ribozyme increased the cleavage rate when its complementary sequence was present in the substrate. Inclusion of the stem-loop at the 3'-end and the extension at the 5'-end of the hairpin ribozyme abolished the positive effect of both antisense units independently. These results may help in the design of hairpin ribozymes for gene silencing.

Base Pairing↗
PubMed1997

[Laparoscopic transperitoneal inguinal hernia repair (TAPP)--complications and results of a prospective study].

Results of a prospective study of 776 TAPP procedures performed on 600 patients are reported. We found rates of 0.5% for intraoperative complications and 1.3% for early-postoperative complications. Late postoperative complications have been observed in an incidence of 4.4% for haematomas, 7.9% for scrotal discomfort, 1.2% for hyperaesthesia and trocar hernias have occurred in 0.9%. The recurrence rate was 3.9%. Results suggest that improvement of the technique of laparoscopic hernia repair may prevent complications and may lower future complication rates.

Adolescent↗
PubMed1994

Self-replication of complementary nucleotide-based oligomers.

The development of non-enzymatic self-replicating systems based on autocatalytic template-directed reactions is a current objective of bioorganic chemistry. Typically, a self-complementary template molecule AB is synthesized autocatalytically from two complementary template fragments A and B. Natural replication of nucleic acids, however, utilizes complementary rather than self-complementary strands. Here we report on a minimal implementation of this type of replication based on cross-catalytic template-directed syntheses of hexadeoxynucleotide derivatives from amino-trideoxynucleotides. In our experiments, two self-complementary and two complementary templates compete for their combinatorial synthesis from four common trimeric precursors. We provide kinetic evidence that cross-catalytic self-replication of complementary templates can proceed with an efficiency similar to that of autocatalytic self-replication of self-complementary templates. We observe selective stimulation of template synthesis, and thus information transfer, on seeding the reaction mixtures with one of four chemically labelled templates bearing the sequence of the reaction products. Our results bring a stage closer the development of schemes that might explain how replicating systems based on nucleic acids arose on the prebiotic Earth.

Biological Evolution↗
PubMed1993

Serotypes, hemagglutinins, siderophore synthesis, and serum resistance of Klebsiella isolates causing human urinary tract infections.

A total of 146 Klebsiella isolates from human asymptomatic bacteriuria (n = 73), cystitis (n = 54), and acute pyelonephritis (n = 19) were examined for the presence of particular virulence factors. Capsular type K2 was the most common serotype observed (13%). This capsule type was prevalent in isolates from asymptomatic bacteriuria and cystitis but not from pyelonephritis. Type 1 fimbriae were found significantly more often in pyelonephritis isolates than among those from asymptomatic and symptomatic lower urinary tract infection (UTI; P < .05), while no marked differences were detected with respect to the distribution of type 3 fimbriae. Serum resistance was more frequent among isolates from symptomatic (26%) than from asymptomatic UTI (18%). Enterochelin was produced by all but 1 of the isolates as determined by a bioassay. In contrast, aerobactin synthesis was rare (3%), with isolates from pyelonephritis showing the highest frequency of aerobactin production (3/19).

Animals↗
PubMed1981

[Intravenous fibrinolytic treatment in chronic ischemic heart disease (author's transl)].

In 13 male patients (mean age 49.1 years) with chronic ischemic coronary heart disease (7 transmural and 2 intramural myocardial infarctions), angina pectoris and signs of ischemia during exercise an intravenous streptokinase therapy was performed. The treatment was installed 18.9 months after infarction or after onset of angina pectoris. Before and after intravenous streptokinase therapy the following parameters were measured: history, heart volume, exercise-ECG, Swan-Ganz pulmonary artery measurements during exercise, aortic and left ventricular pressures, coronary angiography, left ventricular angiography. 1. Angina pectoris disappeared in 1 and became better in 4 patients. In none of the patients angina pectoris became worse. 2. The parameters for ischemia were not changed overall by the therapy. But in single patients signs of exercise-induced ischemia were influenced. 3. Mean values of left ventricular function (EF, LVEDP) were not changed. 4. Angiographic changes were discrete. 5. Complications of therapy and worsening of subjective parameters did not occur. 6. The angina pectoris behaviour in 5 patients (became better) is explained by changes of blood properties. The not-appearance of coronary artery occlusions is explained by the inhibition of platelet aggregation. 7. It is suggested that the effect of intravenous streptokinase therapy should be examined in patients with short-lasting angina pectoris and subgroups, such as initial angina pectoris.

Adult↗
PubMed1977

[The influence of the new beta sympathicolytic agent carazolol on sympathicotonic false regulation (author's transl)].

In 18 patients with tachycardia at rest the effect of treatment with the beta sympathicolytic agent Carazolol was investigated, using Schellong's test, venous occlusion plethysmography, ECG and a questionaire evaluating concomitant effects. A significant reduction in heart rate (about 20 percent) as well as a decrease in systolic blood pressure were observed. No further therapeutical effect was seen during long term treatment. There wer no significant influences on venous occlusion plethysmography and ECG. The patients reported a considerable improvement of their heart complaints.

Adolescent↗