Search PubMed⌕ Search

Biomedical subjects

G Merkel

Publications and source records attributed to G Merkel.

29 records · Page 2Linked to original sources
PubMed1995

Activities and substrate specificity of the evolutionarily conserved central domain of retroviral integrase.

The retroviral integrase (IN) is a virus-encoded enzyme that is essential for insertion of viral DNA into the host chromosome. In order to map and define the properties of a minimal functional domain for this unique viral enzyme, a series of N- and C-terminal deletions of both Rous sarcoma virus (RSV) and human immunodeficiency virus (HIV) INs were constructed. The RSV IN deletion mutants were first tested for their ability to remove two nucleotides from the end of a substrate representing the terminus of viral DNA in order to assess the contribution of N and C regions towards this reaction, referred to as processing. The results suggest that C-terminal amino acids of the intact RSV protein are required to maintain specificity of the processing reaction. Though deficient for processing, the RSV deletion mutants exhibited a secondary endonucleolytic activity that was indistinguishable from that of wild-type IN, demonstrating that all retained some enzymatic activity. RSV, and a larger set of HIV-1, IN deletion mutants were then tested for their ability to perform an intramolecular, concerted cleavage-ligation reaction using an oligodeoxynucleotide substrate that mimics the intermediate viral-host DNA junction found prior to the final step of covalent closure. The composite results from such analyses define a minimal functional central region of approximately 140 amino acids for each enzyme that includes the highly conserved D,D(35)E domain. Results with HIV-1 and HIV-2 IN also indicate that the efficiency of concerted cleavage-ligation depends upon the presence of CA/GT base pairs within the viral component of the DNA substrate at the reaction site. Even the isolated central region of HIV-1 IN exhibited this sequence requirement for optimal activity. We conclude that this evolutionarily conserved central region of IN not only encodes residues that are required for the catalytic activity of the enzyme but also harbors some or all of the determinants responsible for recognition of the CA/GT dinucleotides that are present at the ends of all retroviral DNAs.

Avian Sarcoma Viruses↗
PubMed1995

[Risk for the Rostock water supply from the Warnov river by an old deposit at Schwann?].

Accidents of the city gasworks in the end of the fifties at Schwaan, a small town south of Rostock, resulted in an emission of tar and waste water into the river Warnow, from which the city of Rostock is supplied with drinking water about 20 km downstream. The tar contaminated river sediment (old deposit) covering an area of about 200 m2 has a high pollutant inventory: Steam-distillable phenolic compounds 407 mg/kg in the fresh sediment, polycyclic aromatic hydrocarbons (PAH) 400 to 1100 micrograms/l in the aqueous eluate. The mutagenic potential was detected by the AMES-test. As shown by PAH determinations there were no other pollutant sources in the catchment area, in the tributaries or on other places of the river. The mean PAH concentrations of the river Warnow and his tributaries during 1991 to 1994 were found to be in the range lower than 10 ng/l. Further investigations showed a continuous emission of PAH from the tar laugh in small amounts. An additional emission of pollutants (PAH) and their transportation in the river is expected in the case of sediment disturbances. This emission and their possible consequences are difficult to estimate, even though the seston and the humic substances content of the river seems to reduce the PAH risk. Concluding from our results the probability is very low that pollutants were transported downstream to Rostock and pass the water works but may not totally be excluded. Nevertheless from the viewpoint of care a removal of the old deposit is necessary.

Fresh Water↗
PubMed1994

Indoor factors and IgE levels in children.

The objective of the study was to determine indoor characteristics of households in relation to total serum IgE. In a population-based cross-sectional study, 1096 6-12-year-old children were examined in three East German towns (Eisleben, Hettstedt, and Zerbst). Of the questionnaires, 772 (70.4%) were returned by the parents. Serum IgE of 703 children and urinary cotinine in a random subsample of 224 children were analyzed. Linear regression on log(IgE) adjusted for the main covariates was used to assess indoor risk factors such as room size, and the presence of curtains, carpet, and plants in the child's room. Open-heating facilities indoors, passive smoking, and furniture made of chipboard had the most important effect. A higher urinary cotinine/creatinine ratio was associated with higher total IgE level. Total IGE increased also with the number of persons living in the household, independently of indoor smoking. We conclude that indoor air pollution from smoking and open-heating facilities may increase the IgE levels of children. The role of other factors such as chipboard, which could reflect the emission of formaldehyde, or the number of persons per household, which could reflect viral or helminthic infection, remains to be analyzed.

Air Pollution, Indoor↗
PubMed1993

Histamine release from basophils in childhood: age dependency and inhibition by pertussis infection and pertussis toxin.

The influence of childhood pertussis infection and of purified pertussis toxin on histamine release from human basophil leucocytes was investigated. Three different stimuli, the peptide N-formyl-Met-Phe (NFMP), anti-IgE, and the calciumionophore A23187 were used to challenge the cells. When NFMP was the stimulus, histamine release in the control group (age 0.5-17 years) increased in an age-dependent fashion, whereas anti-IgE and A23187 stimulated release did not vary with age. During the convulsive state of pertussis infection there was a significant reduction of histamine release in response to 10 microM NFMP (from 9.5 +/- 1.4 [n = 21] to 6.7 +/- 1.5 [n = 19], P < 0.05) and in response to 800 and 80 U/ml anti-IgE (from 28.5 +/- 5 [n = 19] to 16.3 +/- 5 [n = 13], P < 0.05, and from 6.9 +/- 1.7 [n = 16] to 2 +/- 0.8 [n = 13], P < 0.01), whereas histamine release stimulated by A23187 was unchanged compared to release in control children. In vitro pretreatment of basophils from healthy children and adults with pertussis toxin also inhibited histamine release. When NFMP was the stimulus, release was completely blocked by pertussis toxin with an IC50 of about 11 ng/ml, whereas anti-IgE stimulated release was only inhibited by 20%-30% and release induced by A23187 was reduced to 40%-50% by toxin treatment. In conclusion we have demonstrated a functional impairment of histamine release during the convulsive state of pertussis and that this inhibition is likely to be mediated by pertussis toxin.

Adolescent↗
PubMed1993

[Isolated proximal fibula fracture in Marfan syndrome].

An isolated fracture of the proximal fibular shaft without associated tibial or ankle injury and without resulting from direct violence is extremely rare. This report presents a case of an unusual isolated proximal fibular fracture (stress-fracture) in a female tennis-player with Marfan-syndrome. The literature is reviewed and diagnosis, treatment and etiology are discussed.

Adult↗
PubMed1992

Requirement for a conserved serine in both processing and joining activities of retroviral integrase.

Retroviruses encode a protein, the integrase (IN), that is required for insertion of the viral DNA into the host cell chromosome. IN alone can carry out the integration reaction in vitro. The reaction involves endonucleolytic cleavage near the 3' ends of both viral DNA strands (the processing step), followed by joining of these new viral DNA ends to host DNA (the joining step). Based on their evolutionary conservation, we have previously identified at least 11 amino acid residues of IN that may be essential for the reaction. Here we report that even conservative replacements of one of these residues, an invariant serine, produce severe reductions in both the processing and joining activities of Rous sarcoma virus IN in vitro. Replacement of the analogous serine of the type 1 human immunodeficiency virus IN had similar effects on processing activity. These results suggest that this single conserved serine is a component of the active site and that one active site is used for both processing and joining. Replacement of this serine with certain amino acids resulted in a loss or reduction in DNA binding activities, while other replacements at this position appeared to affect later steps in catalysis. All of the defective Rous sarcoma virus INs were able to compete with the wild-type protein, which supports a model in which IN functions in a multimeric complex.

Avian Sarcoma Viruses↗
PubMed1990

The avian retroviral IN protein is both necessary and sufficient for integrative recombination in vitro.

The integration of viral DNA into the host cell chromosome is an essential feature of the retroviral life cycle. The integration reaction requires cis-acting sequences at the ends of linear viral DNA and a trans-acting product of the pol gene, the integration protein (IN). Previously, we demonstrated that avian sarcoma-leukosis virus (ASLV) IN is able to carry out the first step in the integration process in vitro: nicking of the ends of linear viral DNA. In this paper, using two independent assays, we demonstrate that IN, alone, is sufficient to carry out the second step: cleavage and joining to the target DNA. These results demonstrate that the retroviral IN protein is an integrase.

Alpharetrovirus↗
PubMed1984

[Psychological aspects of spinal anesthesia. Vasovagal syncope and anxiolytic medication].

In 61 male and female patients, the influence of the preoperative emotional state on vasovagal syncopes and anxiolytic medication during spinal anaesthesia for elective orthopaedic surgery was investigated. Male patients pretended to feel emotionally better than female patients, but had higher rates of anxiolytic medication and vasovagal syncopes. Patients in a bad (n = 8) and in a good emotional state (n = 3) received more anxiolytic medication than those with a mean emotional state. Vasovagal syncopes were registered in patients who pretended to feel good (n = 6), in those who felt bad (n = 4) and only in one patient of the mean group. The factors anxiety and depression were the most responsible for this result. The importance of coping-mechanisms for the development of psychological and psychophysiological reactions is discussed. Vasovagal syncope is interpreted as a psychophysiological reaction. In consequence it needs psychoprophylaxis.

Adolescent↗